1. XX. On the permanent electret
2. Gemant , A. 1933.Liquid Dielectrics, 66–66. New York: Wiley.
3. Gemant , A. 1933.Liquid Dielectrics, 66–66. New York: Wiley. figs. 26 and 48
4. Semenoff , N. and Walther , A. 1928.Elektrisehe Festigkeitslehre, 60–60. Berlin: Springer.