Reversal of wave front in four-photon processes under conditions of two-quantum resonance Bespalov, V. I. ; Betin, A. A. ; Dyatlov, A. I. ; Kulagina, S. N. ; Manishin, V. G. ; Pasmanik, G. A. ; Shilov, A. A. Abstract Publication: Soviet Journal of Experimental and Theoretical Physics Pub Date: August 1980 Bibcode: 1980JETP...52..190B