@article{LJM_2002_10_a1,
     author = {S. A. Grigoryan and R. N. Gumerov},
     title = {On a~covering group theorem and its applications},
     journal = {Lobachevskii journal of mathematics},
     pages = {9--16},
     publisher = {mathdoc},
     volume = {10},
     year = {2002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/LJM_2002_10_a1/}
}