An invariant of simple algebraic groups
  The Rost invariant associated with a simple simply connected algebraic group G is used to define an invariant of strongly inner forms of G. This invariant takes values in a quotient of H^3(k, Q/Z(2)). It is used to prove a generalization of Gille's splitting criterion for groups of type E_6 and E_7. 
R. Skip Garibaldi