  A unified description of channeling radiation (CR) in oriented crystals (OC)
and radiation in the field of an intense plane wave (laser radiation sources -
LRS) is proposed in terms of two Lorentz-invariant parameters. The case of
planar positron channeling (quasi-channeling) and linearly polarized laser wave
is considered in detail up to TeV energies. The crucial difference between LRS
and CR is that in the former case both invariants are independent, while in
channeling they are linearly related to each other. This leads to a strong
limitation on the range of possible values of these invariants in OC. On the
other hand, OC make it possible to study QED processes in strong non-uniform
external fields.
