1. Landolt-Börnstein, “Pysikalisch-Chemische Tabellen”, Erster Ergänzungsband, 160–163; 1927.
2. The Landolt-Börnstein “Tabellen”, (5th edition) list many of the results. Other sources are: V. Posejpal, Ann. Phys., (4), 83, 629–646; 1917. V. Posejpal, J. Phys., (16), 2, 85–92; 1921. A. Pérard, Procés-Verbaux des Séances, x, 16; 1923. A. Zwetsch, Z. Phys., 19, 398–413; 1923. Tausz und Görlacher, Z. tech. Phys., 12, 19–24; 1931. Sears and Barrell, Phil. Trans. Roy. Soc., A, 231, 126–127; 1932. Kösters and Lampe, result obtained in 1932 at the Phys. Techn. Reichsanstalt and privately communicated to me. C. G. Peters, unpublished result obtained in 1917 at the U.S. Bureau of Standards with apparatus different from that used by Meggers and Peters.
3. Ellsworth Huntington, “Earth and Sun”, p. 29, Yale University Press, 1923.