@article{GDZPPN00238700X, title = {On Sonic Limit Lines in the Hodograph Method.}, journal = {Mathematische Zeitschrift}, volume = {67}, year = {1957}, pages = {229-237}, zbl = {0083.41103}, url = {http://dml.mathdoc.fr/item/GDZPPN00238700X} }
Ludford, G.S.S.; Schot, S.H. On Sonic Limit Lines in the Hodograph Method.. Mathematische Zeitschrift, Tome 67 (1957) pp. 229-237. http://gdmltest.u-ga.fr/item/GDZPPN00238700X/