Photometry and spectroscopy of the GRB 970508 optical counterpart by Castro-Tirado, A, Gorosabel, J, Benitez, N, Wolf, C, Fockenbrock, R, Martinez-Gonzalez, E, Kristen, H, Broeils, A, Pedersen, H, Greiner, J, Costa, E, Feroci, M, Piro, L, Frontera, F, Nicastro, L, Palazzi, E, Bartolini, C, Guarnieri, A, Masetti, N, Piccioni, A, Mignoli, M, Wold, M, Lacy, M, Birkle, K, Broadhurst, T