@article{05875574, title = {On the developable ruled surfaces of low smoothness.}, journal = {Sibirskij Matematicheskij Zhurnal}, volume = {50}, year = {2009}, pages = {1163-1175}, zbl = {1224.53010}, language = {en}, url = {http://dml.mathdoc.fr/item/05875574} }
Sabitov, I.Kh. On the developable ruled surfaces of low smoothness.. Sibirskij Matematicheskij Zhurnal, Tome 50 (2009) pp. 1163-1175. http://gdmltest.u-ga.fr/item/05875574/