Lamb shift calculated by simple noncovariant method

The Lamb Shift (LS) of Hydrogenlike atom is evaluated by a simple method of quantum electrodynamics in noncovariant form, based on the relativistic stationary Schr\"odinger equation. An induced term proportional to $\overrightarrow{p}^4$ in the effective Hamiltonian is emphasized. Perturbative calculation of second order leads to the LS of $1S_{1/2}$ state and that of $2S_{1/2}-2P_{1/2}$ states in H atom with the high accuracy within 0.1%