@inproceedings{folke1977convexity,
title={Convexity of means and growth of certain subharmonic functions},
author={Folke Norstad},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203503041705287},
booktitle={Arkiv for Matematik},
volume={16},
number={1},
pages={141-152},
year={1977},
}
Folke Norstad. Convexity of means and growth of certain subharmonic functions. 1977. Vol. 16. In Arkiv for Matematik. pp.141-152. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203503041705287.