The Authorship, Text, and History of the Hymn Dies Irae: With Critical, Historical and Biographical Notes. E-book. Formato PDF Charles F. S. Warren   -  Forgotten Books, 2017  - 

When I first began the work I had by me about a dozen versions, being those best known, with two or three less common which chance had happened to throw in my way and I thought it possible that research might disclose, say an equal number unknown to me, so that the whole, with such notes as it might occur to me to write, would little exceed the size of a large pamphlet.