@article{1214428824, author = {Ambrose, W.}, title = {Convexity of partial differential operators}, journal = {J. Differential Geom.}, volume = {3}, number = {1-2}, year = {1969}, pages = { 125-164}, language = {en}, url = {http://dml.mathdoc.fr/item/1214428824} }
Ambrose, W. Convexity of partial differential operators. J. Differential Geom., Tome 3 (1969) no. 1-2, pp. 125-164. http://gdmltest.u-ga.fr/item/1214428824/