^Miles, Clement A. (1912). Christmas in Ritual and Tradition. from Chapter XIII: Masking, the Mummers’ Play, the Feast of Fools, and the Boy Bishop, "Mr. Chambers's theory is that the ass was a descendant of the cervulus or hobby-buck who figures so largely in ecclesiastical condemnations of Kalends customs."
^"It took place on the kalends of January and was a kind of New Year's festival, at which people exchange strenae (étrennes, 'gifts') dressed up as animals or old women, and danced through the streets singing, the applause of the populace. According to DuCange (s.v. cervulus), sacrilegious songs were sung. This happened even in the vicinity of St. Peter's in Rome".Jung, C. G. (1968). The archetypes and the collective unconscious. Princeton, N.J: Princeton University Press. pp. 257 fn. 3. ISBN0-691-01833-2.