Cita APA

Williams, M. L., & Covington, B. (1999). Distance learning: The essential guide. Thousand Oaks, Calif: Sage.

Chicago Style Citation

Williams, Marcia L., i Barbara Covington. Distance Learning: The Essential Guide. Thousand Oaks, Calif: Sage, 1999.

Cita MLA

Williams, Marcia L., i Barbara Covington. Distance Learning: The Essential Guide. Thousand Oaks, Calif: Sage, 1999.