TY  - JOUR
AU  - Colliot-Thélène, J.-L.
TI  - The Noether-Lefschetz theorem and sums of 4 squares in the rational function field $R(x, y)$
JO  - Compositio Mathematica
PY  - 1993
SP  - 235
EP  - 243
VL  - 86
IS  - 2
PB  - Kluwer Academic Publishers
UR  - http://www.numdam.org./item/CM_1993__86_2_235_0/
LA  - en
ID  - CM_1993__86_2_235_0
ER  -