Colis, O. L. 1. (1972). Programmed instruction in farmers' cooperative. s. n.
Cita Chicago (17th ed.)Colis, Oscar Loyola 1936. Programmed Instruction in Farmers' Cooperative. College, Laguna: s. n, 1972.
Cita MLA (9th ed.)Colis, Oscar Loyola 1936. Programmed Instruction in Farmers' Cooperative. s. n, 1972.
Atenció: Aquestes cites poden no estar 100% correctes.