@inproceedings{lee1962higher,
title={Higher monotonicity properties of certain Sturm-Liouville functions},
author={Lee Lorch, and Peter Szego},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203200465273949},
booktitle={Acta Mathematica},
volume={109},
number={1},
pages={55-73},
year={1962},
}
Lee Lorch, and Peter Szego. Higher monotonicity properties of certain Sturm-Liouville functions. 1962. Vol. 109. In Acta Mathematica. pp.55-73. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203200465273949.