Gilles Pesant Claude-Guy Quimper Louis-Martin Rousseau Meinolf Sellmann The Polytope of Context-Free Grammar Constraints. 223-232 2009 CPAIOR http://dx.doi.org/10.1007/978-3-642-01929-6_17 conf/cpaior/2009 db/conf/cpaior/cpaior2009.html#PesantQRS09