@inproceedings{niels1944on,
title={On the theory of infinite systems of differential equations and their application to the theory of stochastic processes and the perturbation theory of quantum mechanics},
author={Niels Arley, and Vibeke Borchsenius},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203120588474652},
booktitle={Acta Mathematica},
volume={76},
number={3},
pages={261-322},
year={1944},
}

Niels Arley, and Vibeke Borchsenius. On the theory of infinite systems of differential equations and their application to the theory of stochastic processes and the perturbation theory of quantum mechanics. 1944. Vol. 76. In Acta Mathematica. pp.261-322. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203120588474652.