Encyclopedias and dictionaries can be rather difficult to cite because there are a number of points to consider. Is the reference item in print, online, or both. Is it edited, and does the entry in an encyclopedia have an author?
The following are patterns for how you might write a reference list entry for articles from a encyclopedia or an item from a dictionary.
Title of entry. (Year Published). In Title of reference work (xx ed., Vol. xx, pp. xxx-xxx.). Location: Publisher.
Title of entry. (Year Published). In Title of reference work (xx ed., Vol. xx, pp. xxx-xxx.). Retrieved from http://www.xxxxxxxxx
Progressive education. (2013). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/478341/progressive-education
(American Psychological Association, 2010, pp. 79, 204-205; )