Sometimes we ask if the Visconti-Sforza or the Este know or not some book. To resolve these issues, there are two important books:

1. GIULIO BERTONI. LA BIBLIOTECA ESTENSE E LA COLTURA FERRARESE AI TEMPI DEL DUCA ERCOLE I (1471-1505)

read on line.

2. R. SABBADINI. LE SCOPERTE DEI CODICI LATINI E GEECI: secoli XIV e xv

read on line.

Excellent. I was worried that they might not be easy to accessed (especially for people in countries that block Google). But I see Bertoni is here:
https://archive.org/details/bibliotecae ... rt/page/n8

and Sabbadini:
https://archive.org/details/lescoperted ... ft/page/n8

(This post would have been posted in 2010. Somehow it showed up as the beginning of a new thread. in July, 2019. I have restored it to its original thread, although I could not change the posting date.)