Massive star formation by accretion - II. Rotation: how to circumvent the angular momentum barrier? L. Haemmerlé, P. Eggenberger, G. Meynet, A. Maeder, C. Charbonnel and R. S. Klessen A&A, 602 (2017) A17 Published online: 24 May 2017 DOI: 10.1051/0004-6361/201630149