@article{ostwald_2001,  title={On the existence of Levi Foliations},  volume={73},  ISSN={0001-3765},  url={https://doi.org/10.1590/S0001-37652001000100002},  DOI={10.1590/S0001-37652001000100002},  number={1},  journal={Anais da Academia Brasileira de Ciências},  publisher={Academia Brasileira de Ciências},  author={OSTWALD, RENATA N.},  year={2001},  month={Mar},  pages={07–13} }