@article{CM_1993__86_2_235_0, author = {Colliot-Th\'el\`ene, Jean-Louis}, title = {The Noether-Lefschetz theorem and sums of 4 squares in the rational function field $R(x, y)$}, journal = {Compositio Mathematica}, volume = {89}, year = {1993}, pages = {235-243}, mrnumber = {1214459}, zbl = {0774.12002}, language = {en}, url = {http://dml.mathdoc.fr/item/CM_1993__86_2_235_0} }
Colliot-Thélène, J.-L. The Noether-Lefschetz theorem and sums of 4 squares in the rational function field $R(x, y)$. Compositio Mathematica, Tome 89 (1993) pp. 235-243. http://gdmltest.u-ga.fr/item/CM_1993__86_2_235_0/
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