Sing We Now Merrily: A Collection of Elizabethan Rounds from Ravenscroft selected and edited by Edward Bolkovac is an excellent collection of over 75 Thomas Ravenscroft rounds in modern notation. This is a great resource for reenactors, for those interested in musical history, or those that like rounds. There are also good notes and indices by topic, by tonality, by number of parts, and by range. All of this at a reasonable price – currently about $15 new on Amazon. It is also available from Hal Leonard, the distributer, and other sellers.
Originally I thought that the book did not cite which Ravenscroft book each round comes from. However, this information is available in the “Alphabetical List of Rounds” at the end of the book. This is not where I would expect to find it, but at least it is included in Sing We Now Merrily.
The copy I received also has some unevenness in the darkness of the ink on some of the pages.
Otherwise, Sing We Now Merrily is an excellent resource and I highly recommend it.