@article{DE_1972_8_11_a15,
     author = {S. M. Ponomarev},
     title = {Semigroups of the classes $A^{n,\alpha}$ and the abstract {Cauchy} problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2038--2047},
     publisher = {mathdoc},
     volume = {8},
     number = {11},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_11_a15/}
}