A parenthetical citation should use the format ("Entry Name," date) when a publication date is available, or ("Entry Name," n.d.) if no date is present. A signal phrase should follow the same guidelines.
A parenthetical citation example: The bush elephant is also known as the African savanna ("Elephant," n.d.).
A signal phrase example: According to the Encyclopædia Britannica's "Elephant" entry (n.d.), the bush elephant is also known as the African savanna.
In the reference list, begin the encyclopedia listing with the entry name. If a publication date is not available, use "n.d.".
Elephant. (n.d.). In Encyclopædia Britannica online (in italics). Retrieved from http://www.britannica.com/EBchecked/topic/184366/elephant