Schwartz, E., & Colman, C. (1998). Natural energy: From tired to terrific in 10 days. Putnam.
Dyfyniad Arddull ChicagoSchwartz, Erika, and Carol Colman. Natural Energy: From Tired to Terrific in 10 Days. New York: Putnam, 1998.
Dyfyniad MLASchwartz, Erika, and Carol Colman. Natural Energy: From Tired to Terrific in 10 Days. Putnam, 1998.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.