1. Hertz, H. (1892). Untersuchungen ueber die Ausbreitung der Elektrischen Kraft, J.A. Barth. Translated by D.E. Jones as Electric Waves being Researches on the Propagation of Electric Action with Finite Velocity through Space (London: Macmillan, 1893; reprinted New York: Dover, 1962).
2. Hertz, H. (1894). Die Prinzipien der Mechanik in Neuen Zusammenhange Dargestellt, J.A. Barth. Translated by D.E. Jones and J.T. Walley as The Principles of Mechanics presented in a new Form (New York: Dover, 1956).
3. von Helmholtz, H. (1903). Vorträge und Reden, Fünfte Auflage, Zweiter Band, Friedrich Vieweg und Sohn. Translated as The Facts in Perception, in R. S. Cohen and Y. Elkana (eds), Hermann von Helmholtz Epistemological Writings: The Paul Hertz/Moritz Schlick Centenary Edition of 1921 with Notes and Commentary by the Editors (Dordrecht: D. Reidel, 1977), pp. 115–185; on p. 117.
4. von Helmholtz, H. (1968). Das Denken in der Naturwissenschaft, Wissenschaftliche Buchgesellschaft.
5. Lowe, M. (1977). Epistemological Writings: The Paul Hertz/Moritz Schlick Centenary Edition of 1921, with Notes and Commentary by the Editors, Springer. Boston Studies in the Philosophy of Science, 37; First published 1870.