Concealed Wenckebach phenomena in the left bundle-branch.

@article{Friedberg1972ConcealedWP,
  title={Concealed Wenckebach phenomena in the left bundle-branch.},
  author={Hermann Friedberg and L. Schamroth},
  journal={British heart journal},
  year={1972},
  volume={34 4},
  pages={370-3}
}