General encyclopedias attempt to provide a little knowledge about a lot of subjects. The purpose of a general encyclopedia, such as the New Encyclopaedia Britannica, is to present enough information about a subject to get you started on a more detailed search. Specialized encyclopedias, such as The MIT Encyclopedia of the Cognitive Sciences, take a narrower focus, usually covering a field of study or a historical period. Articles in specialized encyclopedias are typically longer than articles in general encyclopedias and offer more detailed coverage of subjects.