Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Pope Sixtus IV:

"

At the beginning of his papacy, in 1471, Sixtus had donated several historically important Roman sculptures that founded a papal collection of art, which would eventually develop into the collections of the Capitoline Museums. He also refounded, enriched and enlarged the Vatican Library.[1] He had Regiomontanus attempt the first sanctioned reorganisation of the Julian calendar[2] and increased the size and prestige of the papal chapel choir, bringing singers and some prominent composers (Gaspar van Weerbeke, Marbrianus de Orto and Bertrandus Vaqueras) to Rome from the north.[citation needed]