@article{MZ_1985__190_173643,
     author = {D.W. Lewis},
     title = {Sums of {Squares} in {Central} {Simple} {Algebras.}},
     journal = {Mathematische Zeitschrift},
     pages = {497--498},
     publisher = {mathdoc},
     volume = {190},
     year = {1985},
     zbl = {0563.16010},
     url = {http://geodesic.mathdoc.fr/item/MZ_1985__190_173643/}
}