@inproceedings{siu1981on,
title={On the upper estimate of the heat kernel of a complete Riemannian manifold},
author={Siu Yuen Cheng, Peter Li, and Shing-Tung Yau},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191224203525842265045},
booktitle={American Journal of Mathematics},
volume={103},
number={5},
pages={1021-1063},
year={1981},
}
Siu Yuen Cheng, Peter Li, and Shing-Tung Yau. On the upper estimate of the heat kernel of a complete Riemannian manifold. 1981. Vol. 103. In American Journal of Mathematics. pp.1021-1063. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191224203525842265045.