Modus ponens and modus tollens in discrete implications

@article{Mas2008ModusPA,
  title={Modus ponens and modus tollens in discrete implications},
  author={Margarita Mas and Miquel Monserrat and Joan Torrens},
  journal={Int. J. Approx. Reasoning},
  year={2008},
  volume={49},
  pages={422-435}
}