Spanish grammar

Spanish grammar is the grammar of the Spanish language (español, castellano), which is a Romance language that originated in north central Spain and is spoken today throughout Spain, some twenty countries in the Americas, and Equatorial Guinea.

Spanish is an inflected language. The verbs are potentially marked for tense, aspect, mood, person, and number (resulting in some fifty conjugated forms per verb). The nouns form a two-gender system and are marked for number. Pronouns can be inflected for person, number, gender (including a residual neuter), and case, although the Spanish pronominal system represents a simplification of the ancestral Latin system.

Spanish was the first of the European vernaculars to have a grammar treatise, Gramática de la lengua castellana, written in 1492 by the Andalusian linguist Antonio de Nebrija and presented to Isabella of Castile at Salamanca.[1]

The Real Academia Española (RAE) traditionally dictates the normative rules of the Spanish language, as well as its orthography.

Formal differences between Peninsular and American Spanish are remarkably few, and someone who has learned the dialect of one area will have no difficulties using reasonably formal speech in the other; however, pronunciation does vary, as well as grammar and vocabulary.

Recently published comprehensive Spanish reference grammars in English include DeBruyne (1996), Butt & Benjamin (2011), and Batchelor & San José (2010).

Verbs

Every Spanish verb belongs to one of three form classes, characterized by the infinitive ending: -ar, -er, or -ir—sometimes called the first, second, and third conjugations, respectively.

A Spanish verb has nine indicative tenses with more-or-less direct English equivalents: the present tense ('I walk'), the preterite ('I walked'), the imperfect ('I was walking' or 'I used to walk'), the present perfect ('I have walked'), the past perfect — also called the pluperfect ('I had walked'), the future ('I will walk'), the future perfect ('I will have walked'), the conditional simple ('I would walk') and the conditional perfect ('I would have walked').

In most dialects, each verb tense has potentially six forms, varying for first, second, or third person and for singular or plural number. In the second person, Spanish maintains the so-called "T–V distinction" between familiar and formal modes of address. The formal second-person pronouns (usted, ustedes) take third-person verb forms.

The second-person familiar plural is expressed in most of Spain with the pronoun vosotros and its characteristic verb forms (e.g. coméis 'you (plural) eat'), while in Latin American Spanish that part of the paradigm is merged with the formal second-person plural (e.g. ustedes comen). In other words, in Latin America, the familiar/formal distinction in the second person is not maintained in the plural.

In many areas of Latin America (especially Central America and southern South America), the second-person familiar singular pronoun is replaced by vos, which frequently requires its own characteristic verb forms, especially in the present indicative, where the endings are -ás, -és, and -ís for -ar, -er, -ir verbs, respectively. See "voseo".

In the tables of paradigms below, the (optional) subject pronouns appear in parentheses.

Present indicative

The present indicative is used to express actions or states of being in a present time frame. For example:

Present indicative forms of the regular -ar verb hablar ('to speak')
Singular Plural
First person (yo) hablo(nosotros/-as) hablamos
Second person familiar (tú) hablas(vosotros/-as) habláis
Second person familiar (vos) hablás/habláis
Second person formal (usted) habla(ustedes) hablan
Third person (él, ella) habla(ellos, ellas) hablan
Present indicative forms of the regular -er verb comer ('to eat')
Singular Plural
First person (yo) como(nosotros/-as) comemos
Second person familiar (tú) comes(vosotros/-as) coméis
Second person familiar (vos) comés/coméis
Second person formal (usted) come(ustedes) comen
Third person (él, ella) come(ellos, ellas) comen
Present indicative forms of the regular -ir verb vivir ('to live')
Singular Plural
First person (yo) vivo(nosotros/-as) vivimos
Second person familiar (tú) vives(vosotros/-as) vivís
Second person familiar (vos) vivís
Second person formal (usted) vive(ustedes) viven
Third person (él, ella) vive(ellos, ellas) viven

Past tenses

Spanish has a number of verb tenses used to express actions or states of being in a past time frame. The two that are "simple" in form (formed with a single word, rather than being compound verbs) are the preterite and the imperfect.

Preterite

The preterite is used to express actions or events that took place in the past, and which were instantaneous or are viewed as completed. For example:

Preterite forms of the regular -ar verb hablar ('to speak')
Preterite of hablar Singular Plural
First person (yo) hablé(nosotros/-as) hablamos
Second person familiar (tú, vos) hablaste(vosotros/-as) hablasteis
Second person formal (usted) habló(ustedes) hablaron
Third person (él, ella) habló(ellos, ellas) hablaron
Preterite forms of the regular -er verb comer ('to eat')
Singular Plural
First person (yo) comí(nosotros/-as) comimos
Second person familiar (tú, vos) comiste(vosotros/-as) comisteis
Second person formal (usted) comió(ustedes) comieron
Third person (él, ella) comió(ellos, ellas) comieron
Preterite forms of the regular -ir verb vivir ('to live')
Singular Plural
First person (yo) viví(nosotros/-as) vivimos
Second person familiar (tú, vos) viviste(vosotros/-as) vivisteis
Second person formal (usted) vivió(ustedes) vivieron
Third person (él, ella) vivió(ellos, ellas) vivieron

Note that (1) for -ar and -ir verbs (but not -er), the first-person plural form is the same as that of the present indicative; and (2) -er and -ir verbs share the same set of endings.

Imperfect or "copretérito"

The imperfect expresses actions or states that are viewed as ongoing in the past. For example:

All three of the sentences above describe "non-instantaneous" actions that are viewed as continuing in the past. The characteristic in the first sentence and the action in the second were continuous, not instantaneous occurrences. In the third sentence, the speaker focuses on the action in progress, not on its beginning or end.

Imperfect forms of the regular -ar verb hablar ('to speak')
Singular Plural
First person (yo) hablaba(nosotros/-as) hablábamos
Second person familiar (tú, vos) hablabas(vosotros/-as) hablabais
Second person formal (usted) hablaba(ustedes) hablaban
Third person (él, ella) hablaba(ellos, ellas) hablaban
Imperfect forms of the regular -er verb comer ('to eat')
Singular Plural
First person (yo) comía(nosotros/-as) comíamos
Second person familiar (tú, vos) comías(vosotros/-as) comíais
Second person formal (usted) comía(ustedes) comían
Third person (él, ella) comía(ellos, ellas) comían
Imperfect forms of the regular -ir verb vivir ('to live')
Singular Plural
First person (yo) vivía(nosotros/-as) vivíamos
Second person familiar (tú, vos) vivías(vosotros/-as) vivíais
Second person formal (usted) vivía(ustedes) vivían
Third person (él, ella) vivía(ellos, ellas) vivían

Note that (1) for all verbs in the imperfect, the first- and third-person singular share the same form; and (2) -er and -ir verbs share the same set of endings.

Using preterite and imperfect together

The preterite and the imperfect can be combined in the same sentence to express the occurrence of an event in one clause during an action or state expressed in another clause. For example:

In all three cases, an event or completed action interrupts an ongoing state or action. For example, in the second sentence, the speaker states that he was in his room (expressed through the imperfect to reflect the ongoing or unfinished state of being there) when the other person "interrupted" that state by entering (expressed through the preterite to suggest a completed action).

Present progressive and imperfect progressive

The present and imperfect progressive both are used to express ongoing, progressive action in the present and past, respectively. For example:

The present progressive is formed by first conjugating the verb estar or seguir, depending on context, to the subject, and then attaching a gerund of the verb that follows. The past (imperfect) progressive simply requires the estar or seguir to be conjugated, depending on context, in imperfect, with respect to the subject.

Forming gerunds

To form the gerund of an -ar verb, replace the -ar of the infinitive with -ando; e.g. jugar, hablar, caminarjugando, hablando, caminando. For -er or -ir verbs, replace the -er or -ir ending with -iendo; e.g. comer, escribir, dormircomiendo, escribiendo, durmiendo (note that dormir undergoes the stem vowel change that is typical of -ir verbs). In -er verbs whose stem ends with a vowel, the i of the -iendo ending is replaced by y: e.g. leer, traer, creerleyendo, trayendo, creyendo. In -ir verbs whose stem ends with e—such as reír and sonreír—the stem vowel e is raised to i (as is typical of -ir verbs), and this i merges with the i of the -iendo ending; e.g. reír, freírriendo, friendo.

Subjunctive

The subjunctive of a verb is used to express certain connotations in sentences such as a wish or desire, a demand, an emotion, uncertainty, or doubt.

Present subjunctive

Normally, a verb would be conjugated in the present indicative to indicate an event in the present frame of time.

If the sentence is trying to express a desire, demand, or emotion, or something similar, in the present tense, the subjunctive is used.

Literally, the sentence above is saying I want that you be very ambitious

The subjunctive is also used to convey doubt, denial, or uncertainty.

In the first two examples, the ideally likable friend has not yet been found and remains an uncertainty, and authors "who write that" are not known to exist. In the third, possibility is not certainty, but rather a conjecture, and the last expresses clear doubt. Thus, subjunctive is used. Some of the phrases and verbs that require sentences to have subjunctive formation include:

Some phrases that require the indicative instead, because they express certainty, include:

To form the subjunctive, first take the present indicative first-person ('yo') form of a verb. For example, the verbs hablar, comer, and escribir (To talk, to eat, to write) --> Yo hablo, yo como, yo escribo Then, replace the ending 'o' with the "opposite ending". The way this works is in the following: If the verb is an -er or -ir verb such as comer, poder, escribir, or compartir, replace the ending o with an 'a' i.e. : Yo como; yo puedo; yo escribo --> Yo coma; yo pueda; yo escriba If the verb is an -ar verb such as caminar, or hablar, replace the ending o with an 'e' i.e. : Yo hablo; yo camino --> Yo hable, yo camine This forms the first-person conjugation. The others are as follows:

Since the vos forms are derived from vosotros the following would be expected (and used in Central America)

However, the Spanish Royal Academy, based in Argentinian usage recommends to use the same forms used for :

Imperfect subjunctive

Today, the two forms of the imperfect subjunctive are largely interchangeable.* The "-se" form derives (as in most Romance languages) from the Latin pluperfect subjunctive, while the "-ra" form derives from the Latin pluperfect indicative. The use of one or the other is largely a matter of personal taste and dialect. Many only use the -ra forms in speech, but vary between the two in writing. Many may spontaneously use either, or even prefer the rarer -se forms. The imperfect subjunctive is formed for basically the same reasons as the present subjunctive, but is used for other tenses and time frames.

Nouns

Spanish has nouns of two genders, masculine and feminine.

Adjectives

Main article: Spanish adjectives

Spanish generally uses adjectives in a similar way to English and most other Indo-European languages. However, there are three key differences between English and Spanish adjectives.

Determiners

Main article: Spanish determiners

Spanish uses determiners in a similar way to English. The main difference is that they "agree" with what they refer to in terms of both number (singular/plural) and gender (masculine/feminine).

Articles

The definite article is equivalent to "the". The indefinite article is equivalent to "a/an, some".

Articles
Definite Indefinite
SingularPluralSingularPlural
Masculine ellosununos
Feminine lalasunaunas
Neuter louno

The "neuter article" lo is used before a masculine singular adjective to form an expression equivalent to an abstract noun, e.g. lo interesante ("the interesting thing, the interesting part").[5][6] Lo may also be used adverbially before an adjective that shows agreement with a noun, being equivalent to the relative adverb 'how', as in lo buenas que son ("how good they [f.pl.] are").[7][8]

When the article el follows either of the prepositions a or de, the two words forms a contraction, al ("to the") or del ("of the, from the"), respectively. Thus: Vamos al parque ("We're going to the park"), Él regresa del cine ("He's returning from the movie theater"), etc. One never says a el or de el in Spanish.

The feminine singular definite article la is replaced by el when directly before a noun that begins with a stressed [a] sound (with or without silent h). Thus el agua, el hambre. The noun remains feminine, as shown by el agua fría. Likewise, the feminine indefinite article una is usually replaced by un in the same circumstances, thus un águila mexicana. When these words are in the plural, the feminine articles are used: las aguas, las águilas.

Demonstratives

Spanish has three kinds of demonstrative, whose use depends on the distance between the speaker and the indicated thing/person. The demonstrative equates to the English terms "this" and "that", although in Spanish the word used must agree for number and gender.

Demonstratives
Proximal Medial Distal
Masculine singular esteeseaquel
Masculine plural estosesosaquellos
Feminine singular estaesaaquella
Feminine plural estasesasaquellas
Neuter singular estoesoaquello

Note that when standing before the noun they qualify — i.e. when used as adjectives — demonstratives never take an accent: esta casa (this house), esos días (those days).

But demonstratives may also stand on their own, instead of the noun they refer to — i.e. as demonstrative pronouns. In that case, they usually carry a written accent: Quiero éste (I want this one).

Neuter demonstratives have the meaning of "this (or that) thing, concept or idea": Eso está bien (That is okay). In certain cases, neuter demonstratives can convey a pejorative connotation: Quita eso de ahí (Take that out of there).

Neuter demonstratives, because of their use, are never used as adjectives, which makes it unnecessary for them ever to take an accent. Moreover, for their indefinite meaning they do not have plural forms.

Possessives

Possessive adjectives (equivalent to English "my", "your", "his", etc.) usually come before the noun they modify and inflect for number but not for gender. The possessive adjectives are:

Possessives
Possessor →
Thing(s) possessed ↓
1st-person singular 2nd-person singular 3rd-person singular 1st-person plural 2nd-person plural 3rd-person plural
Singular mitusunuestrovuestrosu
Plural mistussusnuestrosvuestrossus

Thus:

Spanish also has possessive pronouns that can be used to describe possession of objects already mentioned (analogous to English "mine", "yours", "his", "hers", etc.) and place emphasis on the fact of possession ("this thing of mine", etc.).

Other determiners

Cardinal and ordinal numbers are adjectives of amount (like mucho and poco) and precede nouns (dos animales = 'two animals', primera persona = 'first person'). Primero and tercero drop their final -o before a masculine singular noun, thus el primer libro ('the first book'), el tercer año ('the third year').

The cardinal numbers greater than un/una and the interrogative qué are indeclinable. The indefinite quantifiers, ordinals, un, and cuál are declined as adjectives.

Pronouns

Main article: Spanish pronouns

Spanish has a range of pronouns that in some ways work quite differently from English ones. They include: yo, tú, vos, usted, él, ella, ello, nosotros, vosotros, ustedes, ellos, ellas, esto, eso, aquello etc. Personal pronouns are usually omitted due to context, but it is not rare to see one in written text or in the spoken language, whether it be for emphasis or in cases where there may be some confusion between conjugations.

Adverbs

Spanish adverbs work much like their English counterparts, e.g. muy ("very"), poco ("a little"), lejos ("far"), mucho ("much, a lot"), casi ("almost"), etc. To form adverbs from most adjectives, the adverbial suffix -mente is added to the feminine singular of the adjective, whether or not it differs from the masculine singular. Thus:

The adjectives bueno ("good") and malo ("bad") have irregular adverbial forms: bien ("well") and mal ("badly"), respectively.

As in English, some adverbs are identical to their adjectival counterparts. Thus words such as temprano ("early"), despacio ("slow"), and hondo ("deep") can also mean "early" (as in English, as in "He arrived early") "slowly", and "deeply", respectively.

In series of consecutive adverbs that would each end in -mente on their own, the -mente is dropped from all but the last one, and the others are left as if they were adjectives in the feminine singular. Thus:

There are also a wide variety of adverbial phrases in Spanish, such as a menudo ("often"), en todas partes ("everywhere"), de repente ("suddenly"), por fin ("finally"), and sin embargo ("however, nevertheless").

As with adjectives, the comparative of most adverbs is formed by placing más ("more") or menos ("less") before the adverb. Thus más temprano ("earlier"), más rápidamente ("faster, quicker, more quickly"), menos interesantemente ("less interestingly"), etc. The superlative of most adverbs is formed by placing the neuter article lo before the comparative, although it is usually used with an additional qualifier phrase such as que puedas ("that you can") or de todos ("of all"): lo más rápidamente que puedas ("as quickly as you can", lit. "the most quickly that you can"), lo más interesantemente de todos ("most interestingly of all"), lo menos claramente de ellos ("the least clearly of them"), etc. As with their corresponding adjectival forms, bien ("well") and mal ("badly") have irregular comparitive forms: mejor ("better") and peor ("worse"), respectively, and más and menos are the comparatives of mucho ("much, a lot") and poco ("a little"), respectively.

Prepositions

Main article: Spanish prepositions

Spanish has a relatively large number of prepositions, and does not use postpositions. The following list is traditionally cited:

A, ante, bajo, cabe, con, contra, de, desde, en, entre, hacia, hasta, para, por, según, sin, so, sobre, tras.

Lately, two new prepositions have been added: "durante" and "mediante", usually placed at the end to preserve the list (which is usually learnt by heart by Spanish students).

This list includes two archaic prepositions (so and cabe), but leaves out two new Latinisms (vía and pro) as well as a large number of very important compound prepositions.

Prepositions in Spanish do not change a verb's meaning as they do in English. For example, to translate "run out of water" "run up a bill" "run down a pedestrian" "run in a thief" into Spanish requires completely different verbs, and not simply the use of "correr" ("run") plus the corresponding Spanish prepositions. This is more due to the nature of English phrasal verbs rather than an inherent function of Spanish verbs or prepositions.

Conjunctions

The Spanish conjunctions y ('and') and o ('or') alter their form in both spoken and written language to e and u respectively when followed by an identical vowel sound. Thus, padre e hijo ('father and son'), Fernando e Isabel ('Ferdinand and Isabella'), sujeto u objeto ('subject or object'), vertical u horizontal ('vertical or horizontal').

The change does not take place before the (h)i of a diphthong, as in acero y hierro ('steel and iron'). Nor does the conjunction y change when initial in a question (where it serves to introduce or reintroduce a name as a topic, rather than to link one element with another), as in ¿Y Inés? ('What about Inés?').

When the conjunction o appears between numerals, it is usually spelled with an accent mark (ó), in order to distinguish it from zero (0); thus, 2 ó 3 ('2 or 3') in contrast to 203 ('two-hundred three').

Syntax and syntactic variation

Order of constituents

Spanish word order is generally subject-verb-object (SVO), although verb-subject-object (VSO) and, to a lesser extent, object-verb-subject (OVS) are also used. Thus, to simply say, "My friend wrote the book", one would say (SVO):

Although bare VSO is somewhat rare in declarative independent clauses, VSO is very common in sentences in which something other than the subject or direct object functions as the subject of predication. For example:

In many dependent clauses, VSO order is used to avoid placing the verb in final position:

A sentence in which the direct object is the topic or "theme" (old information), while the subject is part of the comment, or "rheme" (new information), often assumes OVS order; in this case the direct object noun phrase is supplemented with the appropriate direct object pronoun. For example:

Because subject pronouns are often dropped, one will often see sentences with a verb and direct object but no explicitly stated subject.

In questions, VSO order is usual (though not obligatory):

Yes/no questions, regardless of constituent order, are generally distinguished from declarative sentences by context and intonation.

Cleft sentences

A cleft sentence is one formed with the copular verb (generally with a dummy pronoun like "it" as its subject), plus a word that "cleaves" the sentence, plus a subordinate clause. They are often used to put emphasis on a part of the sentence. Here are some examples of English sentences and their cleft versions:

Spanish does not usually employ such a structure in simple sentences. The translations of sentences like these can be readily analyzed as being normal sentences containing relative pronouns. Spanish is capable of expressing such concepts without a special cleft structure thanks to its flexible word order.

For example, if we translate a cleft sentence such as "It was Juan who lost the keys", we get Fue Juan el que perdió las llaves. Whereas the English sentence uses a special structure, the Spanish one does not. The verb fue has no dummy subject, and the pronoun el que is not a cleaver but a nominalising relative pronoun meaning "the [male] one that". Provided we respect the parings of "el que" and "las llaves", we can play with the word order of the Spanish sentence without affecting its structure – although each permutation would, to a native speaker, give a subtly different shading of emphasis.

For example, we can say Juan fue el que perdió las llaves ("Juan was the one who lost the keys") or El que perdió las llaves fue Juan ("The one who lost the keys was Juan"). As can be seen from the translations, if this word order is chosen, English stops using the cleft structure (there is no more dummy "it" and a nominalising relative is used instead of the cleaving word) whilst in Spanish no words have changed.

Here are some examples of such sentences:

Note that it is ungrammatical to try to use just que to cleave such sentences as in English, but using quien in singular or quienes in plural is grammatical.

When prepositions come into play, things become complicated. Structures unambiguously identifiable as cleft sentences are used. The verb ser introduces the stressed element and then there is a nominaliser. Both of these are preceded by the relevant preposition. For example:

This structure is quite wordy, and is therefore often avoided by not using a cleft sentence at all. Emphasis is conveyed just by word order and stressing with the voice (indicated here within bolding):

In casual speech, the complex cleaving pronoun is often reduced to que, just as it is reduced to "that" in English. Foreign learners are advised to avoid this.

In the singular, the subordinate clause can agree either with the relative pronoun or with the subject of the main sentence, though the latter is seldom used. However, in the plural, only agreement with the subject of the main sentence is acceptable. Therefore:

Singular
Plural

Dialectal variations

Forms of address

The use of usted and ustedes as a polite form of address is universal. However, there are variations in informal address. Ustedes replaces vosotros in much of Andalusia, the Canary Islands and Latin America, except in the liturgical or poetic of styles. In some parts of Andalusia, the pronoun ustedes is used with the standard vosotros endings.

Depending on the region, Latin Americans may also replace the singular with usted or vos. The choice of pronoun is a tricky issue and can even vary from village to village. Travellers are often advised to play it safe and call everyone usted.

A feature of the speech of the Dominican Republic and other areas where syllable-final /s/ is completely silent is that there is no audible difference between the second and third person singular form of the verb. This leads to redundant pronoun use, for example, the tagging on of ¿tú ves? (pronounced tuvé) to the ends of sentences, where other speakers would say ¿ves?.

Voseo

Main article: Voseo

Vos was used in medieval Castilian as a polite form, like the French vous and the Italian voi, and it used the same forms as vosotros. This gave three levels of formality:

Whereas vos was lost in standard Spanish, some dialects lost , and began using vos as the informal pronoun. The exact connotations of this practice, called voseo, depend on the dialect. In certain countries there may be socioeconomic implications. El voseo uses the pronoun vos for , but maintains te as an object pronoun and tu and tuyo as possessives.

In voseo, verbs corresponding to vos in the present indicative (roughly equivalent to the English simple present), are formed from the second person plural (the form for vosotros). If the second person plural ends in áis or éis, the form for vos drops the i:

Similarly the verb ser (to be) has:

If the second person plural ends in -ís (with an accent on the í), then the form for vos is identical:

In the imperative, the form for vos is also derived from the second person plural. The latter ends always in -d. So for the form for vos this d is removed, and if the verb has more than one syllable, an accent is added to the last vowel:

The only exception to these rules is in the verb ir (to go), which does not have an imperative form for vos and uses the analogous form of the verb andar, which has a similar meaning, and is regular:

In the present subjunctive, the same rules as for the present indicative apply, though these forms coexist in Argentina with those for the pronoun :

Or:

Other tenses always have the same form for vos as for .

Outside Argentina, other combinations are possible. For instance, people in Maracaibo may use standard vosotros endings for vos (vos habláis, que vos habléis).

Vosotros imperative: -ar for -ad

In Spain, colloquially, the infinitive is used instead of the normative imperative for vosotros. This is not accepted in the normative language.

Non-normative -s on form

A form used for centuries but never accepted normatively has an -s ending in the second person singular of the preterite or simple past. For example, lo hicistes instead of the normative lo hiciste; hablastes tú for hablaste tú. That is the only instance in which the form does not end in an -s in the normative language.

Ladino has gone further with hablates.

Third-person object pronoun variation

The third-person direct-object and indirect-object pronouns exhibit variation from region to region, from one individual to another, and even within the language of single individuals. The Real Academia Española prefers an "etymological" usage, one in which the indirect object function is carried by le (regardless of gender), and the direct object function is carried by la or lo (according to the gender of the antecedent, and regardless of its animacy).

The Academy also condones the use of le as a direct object form for masculine, animate antecedents (i.e. male humans). Deviations from these approved usages are named leísmo (for the use of le as a direct object), and laísmo and loísmo (for the use of la and lo as indirect objects). The object pronoun variation is studied in detail by García & Otheguy (1977).

Queísmo and dequeísmo

Noun clauses in Spanish are typically introduced by the complementizer que, and such a noun clause may serve as the object of the preposition de, resulting in the sequence de que in the standard language. This sequence, in turn, is often reduced colloquially to just que, and this reduction is called queísmo.

Some speakers, by way of hypercorrection (i.e. in an apparent effort to avoid the "error" of queísmo), insert de before que in contexts where it is not prescribed in standard grammar. This insertion of "extraneous" de before que — called dequeísmo — is generally associated with less-educated speakers.

Notes

References

This article is issued from Wikipedia - version of the Wednesday, May 04, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.