@article{langler_2000,  title={Unambiguous assessments of reaction paths for selected pericyclic reactions},  volume={23},  ISSN={0100-4042},  url={https://doi.org/10.1590/S0100-40422000000500021},  DOI={10.1590/S0100-40422000000500021},  number={5},  journal={Química Nova},  publisher={Sociedade Brasileira de Química},  author={Langler, Richard Francis},  year={2000},  month={Sep},  pages={703–705} }