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1 |
The notation of polyphonic music Apel, Willi. - Cambridge, Mass. : Medieval Academy of America, 1949, 4. ed., rev. and with commentary
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2 |
Masters of the keyboard Apel, Willi. - Cambridge, Mass. : Harvard Univ. Pr., 1947
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3 |
Harvard dictionary of music Apel, Willi. - Cambridge, Mass. : Harvard University Press, 1944, 2. print.
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4 |
Harvard dictionary of music Apel, Willi. - Cambridge, Mass. : Harvard Univ. Pr., 1944
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