Sir S. Wilks, Medical Magazine, January, 1894; cf. Clifford Allbutt, "Music, Rhythm, and Muscle," Nature, February 8, 1894.
Bücher, Arbeit und Rhythmus, third edition, 1902; Wundt, Völkerpsychologie, 1900, Part I, p. 265.
Féré deals fully with the question in his book, Travail et Plaisir, 1904, Chapter III, "Influence du Rhythme sur le Travail."