@article{MZM_1972_11_4_a3,
     author = {I. A. Levina},
     title = {On the class number of exact ideals for $Z$-rings in a commutative $Q$-algebra},
     journal = {Matemati\v{c}eskie zametki},
     pages = {381--388},
     publisher = {mathdoc},
     volume = {11},
     number = {4},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1972_11_4_a3/}
}