When using the MLA citation style to cite encyclopedias or dictionaries, include the following information:

• author of article or entry
  
• title of article or entry
• year of publication or copyright
• encyclopedia or dictionary title
• edition (if present)
• volume number and page numbers (unless entries are arranged alphabetically)
• city of publication (unless it is a familiar reference work)
• publishing company (unless it is a familiar reference work)

MLA style does not cite the editior of the reference work. If the article is signed, the author of the article is given first. If it is unsigned, the title is given first. If the encyclopedia or dictionary is arranged alphabetically, the volume and page numbers are omitted. When citing familiar reference works, it is not necessary to give full publication information; list the edition (if present ) and the year of publication.  

Examples:

Please note: the title of the encyclopedia or dictionary is underlined. If 
you are viewing this with Netscape 2.0, the underline will not display. 

Encyclopedia:

Janos, Adam G. "Cold War." Encyclopedia Americana. 1996 ed. 
     
Dictionary: 

"New Wave." Webster's New Collegiate Dictionary. 1983 ed. 

Other: When citing less familiar works, include full publication information.  

Selzner, Adam G., et al. "Religious attitudes in 
        Medical Ethics." Encylopedia of Bioethics.  Ed. Simon Page. 
        6 vols. Chicago: Erlbaum, 1987.