@article{10_2307_2661381,
     author = {Frans Oort},
     title = {Newton polygons and formal groups: {Conjectures} by {Manin} and {Grothendieck}},
     journal = {Annals of mathematics},
     year = {2000},
     volume = {152},
     number = {1},
     doi = {10.2307/2661381},
     zbl = {0991.14016},
     url = {http://geodesic.mathdoc.fr/articles/10.2307/2661381/}
}