Nonlocal operators and distribution amplitudes of definite twist, WW-like relations, BC-like sum rules and power corrections for hard QCD processes

The decomposition of nonlocal operators (and of their matrix elements) into an (infinite) series w.r.t. geometric twist is used to introduce (new) parton distributions, generalized parton distributions and hadron wave functions of definite twist. Their comparision with the conventional distributions (of definite dynamical twist) leads to Wandzura-Wilczek like relations, Burkhardt-Cottingham like sum rules and allows for power corrections of the various distribution amplitudes. Some general aspects are reviewed.