The appearance of acetylcholine during normal labor.

@article{Chang1949TheAO,
  title={The appearance of acetylcholine during normal labor.},
  author={H C Chang and Kyeongbin Lim},
  journal={Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine},
  year={1949},
  volume={72 2},
  pages={413}
}