@inproceedings{l.1973a,
title={A global theory of steady vortex rings in an ideal fluid},
author={L. E. Fraenkel, and M. S. Berger},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203230599854160},
booktitle={Acta Mathematica},
volume={132},
number={1},
pages={13-51},
year={1973},
}
L. E. Fraenkel, and M. S. Berger. A global theory of steady vortex rings in an ideal fluid. 1973. Vol. 132. In Acta Mathematica. pp.13-51. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203230599854160.