Oleg V. Kudinov, Victor L. Selivanov. Definability in the Homomorphic Quasiorder of Finite Labeled Forests. In S. Barry Cooper, Benedikt Löwe, Andrea Sorbi, editors, Computation and Logic in the Real World, Third Conference on Computability in Europe, CiE 2007, Siena, Italy, June 18-23, 2007, Proceedings. Volume 4497 of Lecture Notes in Computer Science, pages 436-445, Springer, 2007. [doi]
Abstract is missing.