To cite an encyclopedia:

1) The author's last name, followed by a comma.
2) The author's first name, followed by a period.
3) The title of the article, followed by a period, in quotation marks.
4) The title of the encyclopedia, underlined, followed by a period.
5) The year of publication of the encyclopedia (if in print), followed by a period.
6) The volume of the encyclopedia (if in print), followed by a period.

Compare your entry to the following examples:

When the author is identified:
Murch, Christopher and William Kilpatrick. "Shakespeare, William."  Collier's Encyclopedia.

        1987. vol. 14.

When the author is not identified:
"Shakespeare, William."  Collier's Encyclopedia. 1987. vol. 14.