Usually encyclopedias are edited and compiled by editors, with contributors writing the different articles. The entry in the reference list will look like that of a chapter in a collected work.
Conteh-Morgan, J. 2003. Modern drama. In: Gikandi, S., ed. Encyclopedia of African literature. London: Routledge. pp. 332-336.
Text reference:
(Conteh-Morgan, 2003:332).
