Clapp, A. L. (1996). National electrical safety code handbook: A discussion of the grounding rules, general rules, and parts 1,2,3, and 4 of the 3rd (1920) through 1997 editions of the National electrical safety code, American national standard C2 (4th ed.). New York, NY: The Institute of Electrical and Electronics Engineers.

Clapp, Allen L. National Electrical Safety Code Handbook: A Discussion of the Grounding Rules, General Rules, and Parts 1,2,3, and 4 of the 3rd (1920) Through 1997 Editions of the National Electrical Safety Code, American National Standard C2. 4th ed. New York, NY: The Institute of Electrical and Electronics Engineers, 1996.

Clapp, Allen L. National Electrical Safety Code Handbook: A Discussion of the Grounding Rules, General Rules, and Parts 1,2,3, and 4 of the 3rd (1920) Through 1997 Editions of the National Electrical Safety Code, American National Standard C2. 4th ed. New York, NY: The Institute of Electrical and Electronics Engineers, 1996.