@inproceedings{william1993extremal,
title={Extremal rational elliptic surfaces in characteristic$p$. II: Surfaces with three or fewer singular fibres},
author={William E. Lang},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203544209323631},
booktitle={Arkiv for Matematik},
volume={32},
number={2},
pages={423-448},
year={1993},
}
William E. Lang. Extremal rational elliptic surfaces in characteristic$p$. II: Surfaces with three or fewer singular fibres. 1993. Vol. 32. In Arkiv for Matematik. pp.423-448. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203544209323631.