@article{10_2307_121037,
     author = {Diego Cordoba},
     title = {Nonexistence of simple hyperbolic blow-up for the quasi-geostrophic equation},
     journal = {Annals of mathematics},
     year = {1998},
     volume = {148},
     number = {3},
     doi = {10.2307/121037},
     zbl = {0920.35109},
     url = {http://geodesic.mathdoc.fr/articles/10.2307/121037/}
}