@article{fontenele_silva_2002,  title={Maximum principles for hypersurfaces with vanishing curvature functions in an arbitrary Riemannian manifold},  volume={74},  ISSN={0001-3765},  url={https://doi.org/10.1590/S0001-37652002000200002},  DOI={10.1590/S0001-37652002000200002},  number={2},  journal={Anais da Academia Brasileira de Ciências},  publisher={Academia Brasileira de Ciências},  author={FONTENELE, FRANCISCO X. and SILVA, SÉRGIO L.},  year={2002},  month={Jun},  pages={199–205} }