@article{10.30755/NSJOM.07233,
     author = {Georgi Dzhelepov},
     title = {Spheres and circles in the tangent space at a point on a {Riemannian} manifold with respect to an indefinite metric},
     journal = {Novi Sad Journal of Mathematics},
     pages = {143 - 150},
     publisher = {mathdoc},
     volume = {48},
     number = {1},
     year = {2018},
     doi = {10.30755/NSJOM.07233},
     url = {http://geodesic.mathdoc.fr/articles/10.30755/NSJOM.07233/}
}