@inproceedings{torbjörn1967convergence,
title={Convergence and invariance questions for point systems in$R$_{1}under random motion},
author={Torbjörn Thedéen},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203439071739083},
booktitle={Arkiv for Matematik},
volume={7},
number={3},
pages={211-239},
year={1967},
}

Torbjörn Thedéen. Convergence and invariance questions for point systems in$R$_{1}under random motion. 1967. Vol. 7. In Arkiv for Matematik. pp.211-239. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203439071739083.