@article{GDZPPN002359316, title = {Smoothness of vector sums of plane convex sets.}, journal = {Mathematica Scandinavica}, volume = {61}, year = {1987}, pages = {239-252}, zbl = {0617.52004}, url = {http://dml.mathdoc.fr/item/GDZPPN002359316} }
Kiselman, Christer O. Smoothness of vector sums of plane convex sets.. Mathematica Scandinavica, Tome 61 (1987) pp. 239-252. http://gdmltest.u-ga.fr/item/GDZPPN002359316/