Gravitational wave recoils in non-axisymmetric Robinson–Trautman spacetimesR. F. Aranha, I. Damião Soares and E. V. ToniniEur. Phys. J. C, 74 10 (2014) 3097DOI: https://doi.org/10.1140/epjc/s10052-014-3097-7