HIGH EFFICIENCY MIDDLE IR PARAMETRIC SUPERRADIANCE IN ZnGeP2 AND GaSe CRYSTALS PUMPED BY AN ERBIUM LASER K.L. VODOPYANOV, L.A. KULEVSKII, A.I. GRIBENYUKOV et K.R. ALLAKHVERDIEV J. Phys. IV France, 01 C7 (1991) C7-391-C7-394 DOI: 10.1051/jp4:19917101