According to Owen Rees (1993), p. 21, "MM 40 is a small choirbook compiled in Portugal, possibly at Braga Cathedral".
According to Owen Ress (1993), the source includes a L'homme armé mass by Francisco Guerrero concordant with a different, later version copied in E-Asa 08 (No.1).
Bibliography of source
How to cite
María Gembero-Ustárroz, "P-Pm 40", Books of Hispanic Polyphony, ed. E. Ros-Fábregas (accession date: 12 Jun 2021), https://hispanicpolyphony.eu/source/31189