Minxia Luo Huacan He A Propositional Calculus Formal Deductive System L<sup>U</sup> of Universal Logic and Its Completeness. 31-41 2005 conf/fskd/2005-1 FSKD (1) http://dx.doi.org/10.1007/11539506_5 db/conf/fskd/fskd2005-1.html#LuoH05