@inproceedings{pavel1998probability,
title={Probability current tornado loops in three-dimensional scattering},
author={Pavel Exner, and P eba},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020133837806573753},
booktitle={Physics Letters A},
volume={245},
pages={35-39},
year={1998},
}

Pavel Exner, and P eba. Probability current tornado loops in three-dimensional scattering. 1998. Vol. 245. In Physics Letters A. pp.35-39. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191020133837806573753.