Παραπομπή APA

Productivity Services International. (1971). Fortune-making in your spare time: Seventy propositions. Productivity services international.

Παραπομπή Chicago Style

Productivity Services International. Fortune-making in Your Spare Time: Seventy Propositions. Bombay: Productivity services international, 1971.

Παραπομπή MLA

Productivity Services International. Fortune-making in Your Spare Time: Seventy Propositions. Productivity services international, 1971.