U. S. Library of Congress. Subject Cataloging Division, Gale Research Company, Library of Congress. Subject Cataloging Division, & Savage, H. (1973). Library of Congress Classification schedules, a cumulation of additions and changes, 1971-1972. Class L: Education. Gale Research Company.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)U. S. Library of Congress. Subject Cataloging Division, Gale Research Company, Library of Congress. Subject Cataloging Division, و Helen Savage. Library of Congress Classification Schedules, a Cumulation of Additions and Changes, 1971-1972. Class L: Education. Detroit, Michigan: Gale Research Company, 1973.
توثيق جمعية اللغة المعاصرة MLA (الإصدار التاسع)U. S. Library of Congress. Subject Cataloging Division, et al. Library of Congress Classification Schedules, a Cumulation of Additions and Changes, 1971-1972. Class L: Education. Gale Research Company, 1973.