Duncan, D. J. (1974). Programmed learning aid for retailing: Modern concepts and practices. Learning Systems Company.
Chicago-Zitierstil (17. Ausg.)Duncan, Delbert J. Programmed Learning Aid for Retailing: Modern Concepts and Practices. Homewood, Illinois: Learning Systems Company, 1974.
MLA-Zitierstil (9. Ausg.)Duncan, Delbert J. Programmed Learning Aid for Retailing: Modern Concepts and Practices. Learning Systems Company, 1974.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.