Task: Question Answering
Input (English): Passage: As one of the earliest centers of book-printing in Europe (see above: History), Strasbourg for a long time held a large number of incunabula—documents printed before 1500—in her library as one of her most precious heritages. After the total destruction of this institution in 1870, however, a new collection had to be reassembled from scratch. Today, Strasbourg's different public and institutional libraries again display a sizable total number of incunabula, distributed as follows: Bibliothèque nationale et universitaire, ca. 2 098 Médiathèque de la ville et de la communauté urbaine de Strasbourg, 394 Bibliothèque du Grand Séminaire, 238 Médiathèque protestante, 94 and Bibliothèque alsatique du Crédit Mutuel, 5. Question: What are incunabula's? 
Output (English): documents printed before 1500