Chitta Baral Vladik Kreinovich Raul Trejo Computational complexity of planning and approximate planning in the presence of incompleteness. 241-267 2000 122 Artif. Intell. 1-2 db/journals/ai/ai122.html#BaralKT00 http://dx.doi.org/10.1016/S0004-3702(00)00043-6