@article{10_1090_S0894_0347_99_00322_7,
     author = {de Jong, A. and Oort, F.},
     title = {Purity of the stratification by {Newton} polygons},
     journal = {Journal of the American Mathematical Society},
     pages = {209--241},
     publisher = {mathdoc},
     volume = {13},
     number = {1},
     year = {2000},
     doi = {10.1090/S0894-0347-99-00322-7},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-99-00322-7/}
}