@article{GDZPPN00125782X, title = {A note on the location of joint discontinuity.}, journal = {Semigroup forum}, volume = {31}, year = {1985}, pages = {173-182}, zbl = {0578.57013}, url = {http://dml.mathdoc.fr/item/GDZPPN00125782X} }
Ruppert, W. A note on the location of joint discontinuity.. Semigroup forum, Tome 31 (1985) pp. 173-182. http://gdmltest.u-ga.fr/item/GDZPPN00125782X/