A. Abel, T. Coquand, and P. Dybjer. Functional and Logic Programming, 9th International Symposium, FLOPS 2008, Ise, Japan, April 14-16, 2008. Proceedings, volume 4989 of Lecture Notes in Computer Science, page 3-13. springer, (2008)
A. Abel, K. Aehlig, and P. Dybjer. Proceedings of the 23rd Conference on the Mathematical
Foundations of Programming Semantics (MFPS XXIII), New Orleans, LA, USA, 11-14 April 2007, page 17-39. Elsevier, (2007)