Experimental search for coherent subthreshold pion production - Erasmus, B; Guet, C; Gillibert, A; Mittig, W; Schutz, Y; Villari, A C C; Kuhn, W; Riess, S; Nifienecker, H; Pinston, J A; Grosse, E; Holzmann, R (Physical Review C, 1991)