@article{Sal'kov2015properties,
author={Sal'kov, N.A.},
title={Properties of Dupin Cyclide and Their Application. Part 3: The Problem of Apollonius},
journal={Geometry & Graphics},
publisher={INFRA-M Academic Publishing LLC.},
year={2015},
pages={3-14},
volume={3},
issue={4},
}