@inproceedings{pascal2013approximation,
title={Approximation numbers of composition operators on the Dirichlet space},
author={Pascal Lefèvre, Daniel Li, Hervé Queffélec, and Luis Rodríguez-Piazza},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203638907293070},
booktitle={Arkiv for Matematik},
volume={53},
number={1},
pages={155-175},
year={2013},
}
Pascal Lefèvre, Daniel Li, Hervé Queffélec, and Luis Rodríguez-Piazza. Approximation numbers of composition operators on the Dirichlet space. 2013. Vol. 53. In Arkiv for Matematik. pp.155-175. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203638907293070.