Ulrich's international periodicals directory 1989-90 / Ulrich's international periodicals directory, 1990-91 : Ulrich's international periodicals directory : Ulrich's international periodicals directory Ulrich's international periodicals directory. Ulrich's periodicals directory : International research centers directory 1984 / The international foundation directory Ulrich's international periodicals directory, 1990-91 : now including Irregular serials & annuals.