Víctor Dalmau, Andrei A. Krokhin, Benoit Larose. First-Order Definable Retraction Problems for Posets and Reflexive Graph. In 19th IEEE Symposium on Logic in Computer Science (LICS 2004), 14-17 July 2004, Turku, Finland, Proceedings. pages 232-241, IEEE Computer Society, 2004. [doi]
Abstract is missing.