%0 Journal Article %A J. Cassels %T On the representation of rational functions as sums of squares %J Acta Arithmetica %D 1964 %P 79-82 %V 9 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/aa-9-1-79-82/ %R 10.4064/aa-9-1-79-82 %G en %F 10_4064_aa_9_1_79_82