Experimental study of Velocity Changing Collisions on Coherent Population Trapping in sodium S. Gozzini, P. Sartini, C. Gabbanini, A. Lucchesini, C. Marinelli, L. Moi, J. H. Xu and G. Alzetta Eur. Phys. J. D, 6 1 (1999) 127-131 Published online: 15 April 1999 DOI: 10.1007/s100530050292