@article{SEMR_2019_16_a139,
     author = {I. A. Krishtal and N. B. Uskova},
     title = {Spectral properties of first-order differential operators with an involution and groups of operators},
     journal = {Sibirskie \`elektronnye matemati\v{c}eskie izvesti\^a},
     pages = {1091--1132},
     publisher = {mathdoc},
     volume = {16},
     year = {2019},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/SEMR_2019_16_a139/}
}