Always look carefully for a byline/author; this is usually at either the beginning or the end of an entry.
With Entry Author
Template
Author, A. A. (Year). Title of entry. In A. Editor (Ed.), Title of reference work (xth ed., Vol. xx, pp. xxx–xxx). Publisher.
Example
Hodges, W. (2006). First-order logic. In D. M. Borchert (Ed.), The encyclopedia of philosophy (2nd ed., Vol. 3, pp. 639–659). Thomson Gale.
(Hodges, 2006)
No Entry Author
Template
Title of entry. (Year). In A. Editor (Ed.), Title of reference work (xth ed., Vol. xx, pp. xxx–xxx). Publisher.
Example
Southeast Asia. (2003). In The new encyclopaedia Britannica: Macropedia (15th ed., Vol. 27, pp. 711–794). Encyclopaedia Britannica.
("Southeast Asia," 2003)