@inproceedings{g´erard2008rigidity,
title={RIGIDITY OF AMALGAMATED PRODUCTS IN NEGATIVE CURVATURE},
author={G´erard Besson, Gilles Courtois, and Sylvain Gallot},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20160909132658438275729},
booktitle={Journal of Differential Geometry},
volume={79},
number={3},
pages={335-387},
year={2008},
}

G´erard Besson, Gilles Courtois, and Sylvain Gallot. RIGIDITY OF AMALGAMATED PRODUCTS IN NEGATIVE CURVATURE. 2008. Vol. 79. In Journal of Differential Geometry. pp.335-387. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20160909132658438275729.