Jürgen Wedekind Some Remarks on the Decidability of the Generation Problem in LFG- and PATR-Style Unification Grammars. 45-52 1995 EACL http://ucrel.lancs.ac.uk/acl/E/E95/E95-1007.pdf db/conf/eacl/eacl1995.html#Wedekind95