@inproceedings{Ghisellini:2012h0, author = "Ghisellini, Gabriele", title = "{GRBs have preferred jet opening angles and bulk Lorentz factors}", doi = "10.22323/1.152.0015", booktitle = "Proceedings of Gamma-Ray Bursts 2012 Conference {\textemdash} PoS(GRB 2012)", year = 2012, volume = "152", pages = "015" }