Westphal, Wilhelm H.; Foland, William D. (1965). "Kleines Lehrbuch der Physik". American Journal of Physics. 33 (4). American Association of Physics Teachers (AAPT): 354. doi:10.1119/1.1971516. ISSN0002-9505.
Westphal, W. H.; Major, Schwab S. (1969). "A Short Textbook of Physics". American Journal of Physics. 37 (9). American Association of Physics Teachers (AAPT): 944. doi:10.1119/1.1975974. ISSN0002-9505.
worldcat.org
Westphal, Wilhelm H.; Foland, William D. (1965). "Kleines Lehrbuch der Physik". American Journal of Physics. 33 (4). American Association of Physics Teachers (AAPT): 354. doi:10.1119/1.1971516. ISSN0002-9505.
Westphal, W. H.; Major, Schwab S. (1969). "A Short Textbook of Physics". American Journal of Physics. 37 (9). American Association of Physics Teachers (AAPT): 944. doi:10.1119/1.1975974. ISSN0002-9505.