Cambridge, Peterhouse, Perne Library, MSS 40, 41, 31 & 32 (471-474): Triplex, Medius, Contratenor and Bassus partbooks from a set of five (the Tenor is missing). Copied in one rapid stint by a single scribe (Thomas Bull?), c. 1540, probably for use at Canterbury Cathedral, newly re-founded by Henry VIII; draws heavily upon repertory from Magdalen College, Oxford. Containing mainly later, Henirican, polyphony, Peterhouse has a late concordance for E75.
Images on DIAMM, which also has Nick Sandon's important PhD thesis on this source.