@book{197401,
	author = {Apel, Willi},
	title = {The notation of polyphonic music, 900-1600.},
	publisher = {Mediaeval Academy of America},
	year = {1953 [i.e. 1961]},
	series = {Mediaeval Academy of America. Publication},
	address = {Cambridge, Mass.},
	edition = {5th ed. rev. and with commentary.},
	note = {"Appendix: transcriptions": [30] p. at end.}
}