@inproceedings{john1975the,
title={The blossoming of Schröder's fourth problem},
author={John Riordan},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203239912017204},
booktitle={Acta Mathematica},
volume={137},
number={1},
pages={1-16},
year={1975},
}