@article{SF_1985__32_134777,
     author = {W. Ruppert},
     title = {A note on the location of joint discontinuity.},
     journal = {Semigroup forum},
     pages = {173--182},
     publisher = {mathdoc},
     volume = {32},
     year = {1985},
     zbl = {0578.57013},
     url = {http://geodesic.mathdoc.fr/item/SF_1985__32_134777/}
}