@article{MZ_1990__204_3_183793,
     author = {Louis Mah\'e},
     title = {Level and {Pythagoras} {Number} of {Some} {Geometric} {Rings.}},
     journal = {Mathematische Zeitschrift},
     pages = {615--629},
     publisher = {mathdoc},
     volume = {204},
     number = {3},
     year = {1990},
     zbl = {0773.11024},
     url = {http://geodesic.mathdoc.fr/item/MZ_1990__204_3_183793/}
}