;--------------------------------- citation -----------------------------------
; preguntas específicas que se pueden hacer con los atributos de citation:
<preguntas_citation> -> (    
   <pregunta_title> | <pregunta_originator> | <pregunta_publisher> |
   (what | which) (<pregunta_publicationDate>)
)
<cont_preguntas_citation> -> (
   <cont_pregunta_title> | <cont_pregunta_originator> | <cont_pregunta_publisher> |
   <cont_pregunta_publicationDate>
)
<infs_citation> -> (
   <inf_publicationDate>
)   
<pregunta_title> -> (
   how many maps are there |
   (what | which) (maps are there | are <cont_pregunta_title>) |
   ?(if there (is | are) | exist)  (a | any | ?(all) ?(the))  (titles of maps | maps)
)
<cont_pregunta_title> -> (
   the ?(titles of) maps
)
<pregunta_originator> -> (
   who (is <cont_pregunta_originator> (that developed | of) | developed) ?the maps
)
<cont_pregunta_originator> -> (
   the ?(name of the) (originator | organization | supplier)
)
<pregunta_publisher> -> (
   who (is <cont_pregunta_publisher> of | published) ?the maps
)
<cont_pregunta_publisher> -> (
   the publisher
)
<pregunta_publicationDate> -> (
   is <cont_pregunta_publicationDate> |
   <cont_pregunta_publicationDate> (does the maps have | have the maps got)
)
<cont_pregunta_publicationDate> -> (
   ?the publication date
)
<inf_publicationDate> -> (
   (with the publication date | which publication date is) <fecha>
)
<atributos_inf_citation> -> (
   title | publisher | (originator | supplier)
)
<atributos_pregunta_citation> -> ( 
   title | (edition | version of the title) | 
   ?geospatial ?data presentation form | series ?name | 
   issue ?(identification | of the series publication) |
   publication (place | city | country)
)