ARTICLE = 'article'
ARTICLE_JOURNAL = 'article-journal'
ARTICLE_MAGAZINE = 'article-magazine'
ARTICLE_NEWSPAPER = 'article-newspaper'
BILL = 'bill'
BOOK = 'book'
BROADCAST = 'broadcast'
CHAPTER = 'chapter'
ENTRY = 'entry'
ENTRY_DICTIONARY = 'entry-dictionary'
ENTRY_ENCYCLOPEDIA = 'entry-encyclopedia'
FIGURE = 'figure'
GRAPHIC = 'graphic'
INTERVIEW = 'interview'
LEGAL_CASE = 'legal_case'
LEGISLATION = 'legislation'
MANUSCRIPT = 'manuscript'
MAP = 'map'
MOTION_PICTURE = 'motion_picture'
MUSICAL_SCORE = 'musical_score'
PAMPHLET = 'pamphlet'
PAPER_CONFERENCE = 'paper-conference'
PATENT = 'patent'
PERSONAL_COMMUNICATION = 'personal_communication'
POST = 'post'
POST_WEBLOG = 'post-weblog'
REPORT = 'report'
REVIEW = 'review'
REVIEW_BOOK = 'review-book'
SONG = 'song'
SPEECH = 'speech'
THESIS = 'thesis'
TREATY = 'treaty'
WEBPAGE = 'webpage'