@article{Lyashkov2017four-dimensional,
author={Lyashkov, A.A. and Panchuk, K.L. and Varepo, L.G.},
title={Four-Dimensional Space’s Hypersurface Mapping Singularity},
journal={Geometry & Graphics},
publisher={INFRA-M Academic Publishing LLC.},
year={2017},
pages={3-10},
volume={5},
issue={3},
}