@article{MZ_1971__120_171509,
     author = {J. Lawson and Bernard Madison},
     title = {On {Congruences} and {Cones.}},
     journal = {Mathematische Zeitschrift},
     pages = {18--24},
     publisher = {mathdoc},
     volume = {120},
     year = {1971},
     zbl = {0206.12004},
     url = {http://geodesic.mathdoc.fr/item/MZ_1971__120_171509/}
}