BeppoSAX confirmation of beamed afterglow emission from GRB 990510 E. Pian, P. Soffitta, A. Alessi, L. Amati, E. Costa, F. Frontera, A. Fruchter, N. Masetti, E. Palazzi, A. Panaitescu and P. Kumar A&A, 372 2 (2001) 456-462 Published online: 15 June 2001 DOI: 10.1051/0004-6361:20010471