University of the Philippines (Los Baños). Learning Resource Center, Panopio, R. G., Elec, B. M., Lerios, M. C., Belarmino, M. C., & Velasquez, G. A. (1999). Workbook for PSI for college algebra. Learning Resource Center.

University of the Philippines (Los Baños). Learning Resource Center, Rolando G. Panopio, Bernarda M. Elec, Marcelina C. Lerios, Myrna C. Belarmino, and Gemma A. Velasquez. Workbook for PSI for College Algebra. Quezon City: Learning Resource Center, 1999.

University of the Philippines (Los Baños). Learning Resource Center, et al. Workbook for PSI for College Algebra. Learning Resource Center, 1999.