1. Okerson, Ann, Of Making Many Books There is No End: Report on Serial Prices for the Association of Research Libraries, Eastchester, NY: Ann Okerson, April 1989, p. 10.
2. ISO/9230 Draft International Standard - Determination of price indexes for books and serials purchased by libraries, Berlin , International Organization for Standardization , 1988, p. 3.
3. American National Standard for Library and Information Sciences and Related Publishing Practices - Library Materials-Criteria for Price Indexes (Z39.20-1983), N.Y. American National Standards Institute, Inc.,1983, p. 7.