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. Algebra, Meaning and Computation. Essays Dedicated to Joseph A. Goguen on the Occasion of His 65th Birthday, volume 4060 of Lecture Notes in Computer Science, page 124-149. Springer; Berlin; http://www.springer.de, (2006)