UPPER LIMITS TO THE HIGH-ENERGY GAMMA-RAY AND HARD X-RAY FLUX FROM SN-1987A ON DAY 55 - SOOD,RK; THOMAS,JA; WALDRON,L; MANCHANDA,RK; UBERTINI,P; BAZZANO,A; LAPADULA,C; STAUBERT,R; KENDZIORRA,E; ROCHESTER,GK; SUMNER,TJ; FRYE,G; et al. (MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1988)