Oleg V. Kudinov, Victor L. Selivanov. Undecidability in the Homomorphic Quasiorder of Finite Labeled Forests. In Arnold Beckmann, Ulrich Berger, Benedikt Löwe, John V. Tucker, editors, Logical Approaches to Computational Barriers, Second Conference on Computability in Europe, CiE 2006, Swansea, UK, June 30-July 5, 2006, Proceedings. Volume 3988 of Lecture Notes in Computer Science, pages 289-296, Springer, 2006. [doi]
Abstract is missing.