1º_ Relating to reference documents, especially those that give rise to new reports, works, theses. 2º_ It is the name given to a film or series that does not show fictional recreations but real images of the events it narrates. In addition to the artistic value, they have informative and journalistic relevance. The term is attributed to the Scottish film director, producer and critic John Grierson, who gave cinema an educational character, capable of modifying society by showing it as it is.