This paper examines the free online encyclopedia Wikipedia and its novel model of knowledge-certification in making reference works. The traditional model of reference works operates in a closed and centralized structure, and obtains it authority from institutionalized publishing practices and from authors and reviewers with academic credentials. The Wikipedia model is an open and loose structure which encourages large-scale collaboration by volunteer editors, with or without academic credentials, and often anonymous. Nevertheless, Wikipedia has a set of behavior and content policies and guidelines to ensure its quality. For example, good editors should be able to provide citations and references, which are usually published sources. Although it does not privilege experts over lay editors, Wikipedia does not necessarily disrespect expertise, but only insists that content should be verifiable independent of the credentials of its provider.