Koji Nakazawa Makoto Tatsuta Yukiyoshi Kameyama Hiroshi Nakano Undecidability of Type-Checking in Domain-Free Typed Lambda-Calculi with Existence. 478-492 2008 CSL http://dx.doi.org/10.1007/978-3-540-87531-4_34 conf/csl/2008 db/conf/csl/csl2008.html#NakazawaTKN08