@article{Loyer09,
 Author = {Yann Loyer and Umberto Straccia},
 Journal = {Annals of Mathematics and Artificial Intelligence},
 Number = {3-4},
 Pages = {389-417},
 Title = {Approximate Well-Founded Semantics, Query Answering and Generalized Normal Logic Programs over Lattices},
 Volume = {55},
 Year = {2009}}