  John Morgan and G,Tian pointed out a mistake in the concluding argument for
our paper entitled "$C_1$ in [2] is zero", which was recently published in
arXiv:1512.02098. We hereby acknowledge this mistake and correct the
computation, leading to the conclusion that $C_1$ is non-zero and that their
reference [2] does indeed fully address and resolve the issue raised by the
counter-example which we provided in [3] to the inequality (19.10) in their
monograph [1].
