We introduce the notion of (Weak) Corestriction Principle and prove some relations between the validity of this principle for various connecting maps in non-abelian Galois cohomology over fields of characteristic 0. We also prove the validity of Weak Corestriction Principle for images of coboundary maps $\H^1(k,G) \to \H^2(k,T)$, where $T$ is a finite commutative $k$-group of multiplicative type, $G$ is adjoint, semisimple and contains only almost simple factors of certain inner types.
Homology, Homotopy and Applications, Vol. 5(2003), No. 1, pp. 219-249