@article{IIGUM_2015_12_a3,
     author = {O. V. Zubkov},
     title = {Some closed classes unary generated ultra funktions},
     journal = {The Bulletin of Irkutsk State University. Series Mathematics},
     pages = {35--48},
     publisher = {mathdoc},
     volume = {12},
     year = {2015},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IIGUM_2015_12_a3/}
}