@article{articleda1384cc,
title   = {Submanifolds with nonpositive extrinsic curvature},
author = {Canevari, Samuel and Freitas, Guilherme Machado de and Manfio, Fernando},
year = {2017},
doi = {10.1007/s10231-016-0578-3},
journal   = {Annali di Matematica Pura ed Applicata}
}