@article{MZ_1980__171_172919,
     author = {Bruce Reznick and M.-D. Choi and T.-Y. Lam},
     title = {Real {Zeros} of {Positive} {Semidefinite} {Forms.} {I.}},
     journal = {Mathematische Zeitschrift},
     pages = {1--26},
     publisher = {mathdoc},
     volume = {171},
     year = {1980},
     zbl = {0415.10018},
     url = {http://geodesic.mathdoc.fr/item/MZ_1980__171_172919/}
}