M. Roggenbach, L. Schröder, und T. Mossakowski. Recent Developments in Algebraic Development Techniques, 14th International Workshop, WADT'99, Volume 1827 von Lecture Notes in Computer Science, Seite 146--161. Springer; Berlin; http://www.springer.de, (2000)
C. Olds, A. Lax, und G. Davidoff. Anneli Lax New Mathematical Library Mathematical Association of America, Washington, DC, (2000)Appendix I by Peter D. Lax.