David Gries. Monotonicity in Calculational Proofs. In Ernst-Rüdiger Olderog, Bernhard Steffen, editors, Correct System Design, Recent Insight and Advances, (to Hans Langmaack on the occasion of his retirement from his professorship at the University of Kiel). Volume 1710 of Lecture Notes in Computer Science, pages 79-85, Springer, 1999. [doi]
Abstract is missing.