T. Mossakowski, C. Maeder, and K. Lüttich. TACAS 2007, volume 4424 of Lecture Notes in Computer Science, page 519-522. Springer-Verlag Heidelberg, (2007)
T. Mossakowski, Kolyang, and B. Krieg-Brückner. Recent Trends in Algebraic Development Techniques, 12th International Workshop, WADT’97, 1376, page 333-348. Springer-Verlag; D-69121 Heidelberg, Germany; http://www.springer.de, (1998)