Allen, R. Y., & Spohn, R. F. W. (1987). Selling Dynamics. McGraw-Hill.
Dyfyniad Arddull ChicagoAllen, Robert Y., and Robert F Wilson Spohn. Selling Dynamics. New York: McGraw-Hill, 1987.
Dyfyniad MLAAllen, Robert Y., and Robert F Wilson Spohn. Selling Dynamics. McGraw-Hill, 1987.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.