See the Life of Nicholas V. by two contemporary authors, Janottus Manettus (tom. iii. P. ii. p. 905 - 962), and Vespasian of Florence (tom. xxv. p. 267 - 290), in the collection of Muratori; and consult Tiraboschi (tom. vi. P. i. p. 46 - 52, 109), and Hody in the articles of Theodore Gaza, George of Trebizond, etc.