K. Szymiczek, Grothendieck groups of quadratic forms and G-equivalence of fields

(Proc. Cambridge Phil. Soc.73 (1973), 29–36

Theorem 2 of the paper has been proved under stronger hypotheses than stated explicitly. Denote by g2(k) the subset g(k) = k*/k*2 represented by the form (1, 1) over k and by U2(k) the set of equivalence classes of 2-dimensional universal quadratic forms over k.