- Dan E. Willard:
Efficient Processing of Relational Calculus Expressions Using Range Query Theory. SIGMOD Conference 1984: 164-175 - Beatrice Yormark:
SIGMOD'84, Proceedings of Annual Meeting, Boston, Massachusetts, USA, June 18-21, 1984. ACM Press 1984, ISBN 978-0-89791-128-3 [contents]