@article{MZ_1986__193_173786,
     author = {R. Baeza and D. Leep and M. O'Ryan},
     title = {Sums of {Squares} of {Linear} {Forms.}},
     journal = {Mathematische Zeitschrift},
     pages = {297--306},
     publisher = {mathdoc},
     volume = {193},
     year = {1986},
     zbl = {0598.10032},
     url = {http://geodesic.mathdoc.fr/item/MZ_1986__193_173786/}
}