Hierarchical relationships in bibliographic descriptions: Ahmed H. Helal and Joachim W. Weiss (eds), (INTERMARAC software-subgroup seminar, no. 4, 25–27 March 1981) (Publications of Essen University library, ISSN 0721-0469; Vol. 2) Essen, Federal Republic of Germany: Gesamthochschulbibliotek Essen, 1981. 424p. ISBN: 3-922602-002. (No charge)