@article{ASNSP_1975_4_2_4_557_0, author = {Stormark, Olle}, title = {A note on a paper by {Andreotti} and {Hill} concerning the {Hans} {Lewy} problem}, journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze}, pages = {557--569}, publisher = {Scuola normale superiore}, volume = {Ser. 4, 2}, number = {4}, year = {1975}, zbl = {0313.32019}, mrnumber = {477151}, language = {en}, url = {http://www.numdam.org/item/ASNSP_1975_4_2_4_557_0/} }