@article{02216475, title = {On boundaries of unions of sets with positive reach.}, journal = {Beitr\"age zur Algebra und Geometrie}, volume = {46}, year = {2005}, pages = {397-404}, zbl = {1097.53050}, language = {en}, url = {http://dml.mathdoc.fr/item/02216475} }
Rataj, J. On boundaries of unions of sets with positive reach.. Beiträge zur Algebra und Geometrie, Tome 46 (2005) pp. 397-404. http://gdmltest.u-ga.fr/item/02216475/