@article{TM2_2011_XIV_2_a5,
     author = {Sini\v{s}a T. Vre\'cica},
     title = {Euler formula and maps on surfaces},
     journal = {The Teaching of Mathematics},
     pages = {107 },
     publisher = {mathdoc},
     volume = {XIV},
     number = {2},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TM2_2011_XIV_2_a5/}
}