Van Couvering, J. A., & Kay, R. F. (2000). Oligocene. In E. Delson, I. Tattersall, J. A. VanCouvering, & A. Brooks (Eds.), Encyclopedia of Evolution and Prehistory, 2nd Edition (pp. 489–490). New York: Garland Pub. Co.

Van Couvering, J. A., and R. F. Kay. “Oligocene.” In Encyclopedia of Evolution and Prehistory, 2nd Edition, edited by E. Delson, I. Tattersall, J. A. VanCouvering, and A. Brooks, 489–90. New York: Garland Pub. Co, 2000.

Van Couvering JA, Kay RF. Oligocene. In: Delson E, Tattersall I, VanCouvering JA, Brooks A, editors. Encyclopedia of Evolution and Prehistory, 2nd Edition. New York: Garland Pub. Co; 2000. p. 489–90.

Van Couvering, J. A., and R. F. Kay. “Oligocene.” Encyclopedia of Evolution and Prehistory, 2nd Edition, edited by E. Delson et al., Garland Pub. Co, 2000, pp. 489–90.

Van Couvering JA, Kay RF. Oligocene. In: Delson E, Tattersall I, VanCouvering JA, Brooks A, editors. Encyclopedia of Evolution and Prehistory, 2nd Edition. New York: Garland Pub. Co; 2000. p. 489–490.