@article{DAN_1970_194_1_a4,
     author = {N. H. Ibragimov},
     title = {Conformal invariance and {Huygens'} principle},
     journal = {Doklady Akademii Nauk},
     pages = {24--27},
     publisher = {mathdoc},
     volume = {194},
     number = {1},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_194_1_a4/}
}