@article{AM_2000_151_3_a1,
     author = {Enrique R. Pujals and Mart{\'\i}n Sambarino},
     title = {Homoclinic tangencies and hyperbolicity for surface diffeomorphisms},
     journal = {Annals of mathematics},
     publisher = {mathdoc},
     volume = {151},
     number = {3},
     year = {2000},
     url = {http://geodesic.mathdoc.fr/item/AM_2000_151_3_a1/}
}