@article{Gül_1999, title={An application for the Gauss-Bonnet theorem}, volume={13}, url={https://revistas.pucp.edu.pe/index.php/promathematica/article/view/8146}, number={25-26}, journal={Pro Mathematica}, author={Gül, Erdal}, year={1999}, month={feb.}, pages={11-16} }