@article{MS2_1990__66_1_167106,
     author = {Jan Boman},
     title = {The sum of two plane convex {C...} sets is not always {C...}},
     journal = {Mathematica Scandinavica},
     pages = {216--224},
     publisher = {mathdoc},
     volume = {66},
     number = {1},
     year = {1990},
     zbl = {0739.52003},
     url = {http://geodesic.mathdoc.fr/item/MS2_1990__66_1_167106/}
}