@article{guedes_markenzon_2005,  title={Directed hypergraph planarity},  volume={25},  ISSN={0101-7438},  url={https://doi.org/10.1590/S0101-74382005000300005},  DOI={10.1590/S0101-74382005000300005},  number={3},  journal={Pesquisa Operacional},  publisher={Sociedade Brasileira de Pesquisa Operacional},  author={Guedes, André Luiz Pires and Markenzon, Lilian},  year={2005},  month={Sep},  pages={383–390} }