@article{SM_2001_192_9_a1,
     author = {V. V. Volchkov},
     title = {Theorems on ball mean values in symmetric spaces},
     journal = {Sbornik. Mathematics},
     pages = {1275--1296},
     publisher = {mathdoc},
     volume = {192},
     number = {9},
     year = {2001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2001_192_9_a1/}
}