@inproceedings{antonio2012the,
title={The Chern–Osserman inequality for minimal surfaces in a Cartan–Hadamard manifold with strictly negative sectional curvatures},
author={Antonio Esteve, and Vicente Palmer},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203636888705055},
booktitle={Arkiv for Matematik},
volume={52},
number={1},
pages={61-92},
year={2012},
}

Antonio Esteve, and Vicente Palmer. The Chern–Osserman inequality for minimal surfaces in a Cartan–Hadamard manifold with strictly negative sectional curvatures. 2012. Vol. 52. In Arkiv for Matematik. pp.61-92. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203636888705055.