^Drbal, Karel. Patenti Spis c. 91304. (Prague: 1959).
^Toth, Max, and Greg Nielson. Pyramid Power. (New York: Warner Destiny, 1976). 165.
^Toth, Max, and Greg Nielson. Pyramid Power. (New York: Warner Destiny, 1976). 177.
^De Mattia, Joan Ann. “Enjoying the Fruits of Pyramid Energy.” Pyramid Power, edited by Max Toth and Greg Nielson. (New York: Warner Destiny, 1976). 198.
^Drbal, Karel. “The Struggle for the Pyramid Patent.” Pyramid Power, edited by Max Toth and Greg Nielson. (New York: Warner Destiny, 1976). 143.