@article{Nikiforov2013constructing,
author={Nikiforov, V.. and Maltseva, E..},
title={Constructing method related to technical drawing of sphere surface with overlay of sphere’s own and falling shadows},
journal={Geometry & Graphics},
publisher={INFRA-M Academic Publishing LLC.},
year={2013},
pages={13-15},
volume={1},
issue={3},
}