The power P can be shown to be Lorentz invariant. Any relativistic generalization of the Larmor formula must therefore relate P to some other Lorentz invariant quantity. The quantity | p ˙ ˙ | 2 appearing in the nonrelativistic formula suggests that the relativistically correct formula should include the Lorentz scalar found by taking the inner product of the four-acceleration a = dp / dτ with itself [here p = (γmc, γm v) is the four-momentum ]. The correct relativistic generalization of the Larmor formula is (in CGS units)