de http://en.wikipedia.org/wiki/File:Gregorian_chant.gif/Image:Gregorian_chant.gif
Missa XI Factor Orbis ( in dominicis infra annum ), comienzo de Kyrie eleison versión B
Siglo XIV-XVI
de Graduale Romanum Sacrosanctae Romanae Ecclesiae , Solesmes MCMLXXIX, p. 748