  Bilocal light-ray operators which are Lorentz scalars, vectors or
antisymmetric tensors, and which appear in various hard scattering QCD
processes, are decomposed into operators of definite twist. These operators are
harmonic tensor functions and their Taylor expansion consists of (traceless)
local light-cone operators with span irreducible representations of the Lorentz
group with definite spin j and common geometric twist (= dimension - spin).
Some applications concerning the nonforward matrix elements of these operators
and the generalization fo conformal light-cone operators of definite twist is
considered. The group theoretical background of the method has been made clear.
