@inproceedings{adrian2006amalgamated,
title={Amalgamated free products of weakly rigid factors and calculation of their symmetry groups},
author={Adrian Ioana, Jesse Peterson, and Sorin Popa},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203351583487700},
booktitle={Acta Mathematica},
volume={200},
number={1},
pages={85-153},
year={2006},
}

Adrian Ioana, Jesse Peterson, and Sorin Popa. Amalgamated free products of weakly rigid factors and calculation of their symmetry groups. 2006. Vol. 200. In Acta Mathematica. pp.85-153. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203351583487700.