Rare and valuable prints were protected starting at an early stage by keeping them in the special rare books collection. This collection of over 4,300 volumes has in the meantime been exceeded more than tenfold by the still growing reserve. Starting in 1973, the general holdings of the library have been systematically searched for books from the 16th to the 19th century containing original graphic artists' prints, first editions and rare books of poetry and fiction, of the history of science and culture.