@article{IVM_1968_3_a10,
     author = {Yu. I. Romanov},
     title = {Comparison of the strength of certain $\Delta\Sigma$-operations in connection with the generalization of certain multiple separability theorems.},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {80--85},
     publisher = {mathdoc},
     number = {3},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1968_3_a10/}
}