Evidence for diverse optical emission from gamma-ray burst sources 由 Pedersen, H, Jaunsen, A, Grav, T, Ostensen, R, Andersen, M, Wold, M, Kristen, H, Broeils, A, Naslund, M, Fransson, C, Lacy, M, Castro-Tirado, A, Gorosabel, J, Espinosa, J, Perez, A, Wolf, C, Fockenbrock, R, Hjorth, J