@article{Ushkho2014on,
author={Ushkho, A.. and Tlyachev, V.. and Ushkho, D..},
title={On the number invariant line of planar polynomial differential systems from above estimate},
journal={Actual directions of scientific researches of the XXI century: theory and practice},
publisher={FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov},
year={2014},
pages={121-124},
volume={2},
issue={4},
}