Write the title of the entry in the encyclopedia. Exclude any articles (i.e., "the"). For example, if you looked up the Civil War, then write "Civil War." Don't italicize this title, and don't enclose it in quotes.
Note the publication date, which is the year when the encyclopedia was published. You can find this information on the copyright page, at the very beginning of the book. Put the year in parentheses, and after the parentheses, write a period.
Write the word "In"; next, write the name of the encyclopedia's editor, if there is one. Check on the title page (at the front of the book, usually just after the copyright page). In your bibliographic entry, write the editor's first initial and then his last name, followed by a parenthesis containing the abbreviation for editor (Ed.) and a comma. Some encyclopedias have no editor, only a publisher; if that is the case, you can skip writing the editor's name, but still write the word "In."
Write the name of the encyclopedia in italics. Only capitalize the first word and any proper nouns. Do not place a period at the end of the title.
Write, in parentheses, three things (if available): The number of the encyclopedia's edition, followed by "ed.," (including the period and comma); the number or letter(s) of the specific volume you are consulting, preceded by "Vol." (including the period), followed by a comma; and the page number(s) of the specific entry you are citing, preceded by "pp." (including the period). After the concluding parenthesis, place a period.
Write the location of the publisher and then the name of the publisher, separated by a colon. (To find this information, look on the copyright and title pages.)
Write the first few words of the entry's title in the place where you would normally write the author's name. At the end of the sentence in which you mention or quote the encyclopedic entry, place a set of parentheses. The first thing in the parentheses should be this short version of the entry's title, followed by a comma.
Note the encyclopedia's year of publication.
Add another comma and then specify the exact page number you are referring to, if you have quoted from the encyclopedia or if you are mentioning a specific fact that can only be found in one part of the entry. If you don't need to specify the page number, conclude the parentheses after Step 2.