Spinning up black holes with super-critical accretion flows A. Sądowski, M. Bursa, M. Abramowicz, W. Kluźniak, J.-P. Lasota, R. Moderski and M. Safarzadeh A&A, 532 (2011) A41 Published online: 20 July 2011 DOI: 10.1051/0004-6361/201116702