4MID:
reference: An Activin A/BMP2 Chimera Displays Bone Healing Properties Superior to Those of BMP2., Yoon BH, Esquivies L, Ahn C, Gray PC, Ye SK, Kwiatkowski W, Choe S, J Bone Miner Res. 2014 Apr 1. doi: 10.1002/jbmr.2238. PMID: 24692083

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