Protostellar collapse: rotation and disk formation W. M. Tscharnuter, J. Schönke, H.-P. Gail, M. Trieloff and E. Lüttjohann A&A, 504 1 (2009) 109-113 Published online: 09 July 2009 DOI: 10.1051/0004-6361/200912120