@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/