Παραπομπή APA

Ryan, W. T. (1971). Programmed learning aid for principles of marketing. Learning systems company.

Παραπομπή Chicago Style

Ryan, William T. Programmed Learning Aid for Principles of Marketing. Illinois: Learning systems company, 1971.

Παραπομπή MLA

Ryan, William T. Programmed Learning Aid for Principles of Marketing. Learning systems company, 1971.