@article{AA_1998_10_2_a6,
     author = {A. S. Matveev},
     title = {On the convexity of the images of quadratic mappings},
     journal = {Algebra i analiz},
     pages = {159--196},
     publisher = {mathdoc},
     volume = {10},
     number = {2},
     year = {1998},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AA_1998_10_2_a6/}
}