@inproceedings{a.1954solutions,
title={Solutions of differential equations as analytic functionals of the coefficient functions},
author={A. D. Michal, and D. H. Hyers},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203139055481790},
booktitle={Acta Mathematica},
volume={91},
number={1},
pages={75-86},
year={1954},
}
A. D. Michal, and D. H. Hyers. Solutions of differential equations as analytic functionals of the coefficient functions. 1954. Vol. 91. In Acta Mathematica. pp.75-86. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203139055481790.