@article{RM_1990_45_2_a13,
     author = {S. M. Natanzon},
     title = {Supercoverings, $SNEC$-groups, and interior groups of {Riemann} and {Klein} supersurfaces},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {225--226},
     publisher = {mathdoc},
     volume = {45},
     number = {2},
     year = {1990},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1990_45_2_a13/}
}