by Markus Rost (5 pages)
C. R. Acad. Sci. Paris Sér. I Math. 313 (1991), no. 12, 823-827.
We sketch the construction of an invariant in H3(F,Z/3) for simple exceptional Jordan algebras over a field F with Char F different from 2 and 3. This invariant vanishes if and only if the algebra has zero divisors. If F contains the 3-rd roots of unity, the invariant can be lifted to Milnor's K-group K3M(F)/3.
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