@inproceedings{andreas2020topology,
title={Topology change of level sets in Morse theory},
author={Andreas Knauf, and Nikolay Martynchuk},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20220311100752085888946},
booktitle={Arkiv for Matematik},
volume={58},
number={2},
pages={333-356},
year={2020},
}

Andreas Knauf, and Nikolay Martynchuk. Topology change of level sets in Morse theory. 2020. Vol. 58. In Arkiv for Matematik. pp.333-356. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20220311100752085888946.