%0 Journal Article %A Diego Cordoba %T Nonexistence of simple hyperbolic blow-up for the quasi-geostrophic equation %J Annals of mathematics %D 1998 %V 148 %N 3 %U http://geodesic.mathdoc.fr/articles/10.2307/121037/ %R 10.2307/121037 %F 10_2307_121037