@article{MZM_1992_51_2_a22,
     author = {V. V. Ryzhikov},
     title = {An estimate of the entropy of a class of $Z^2$-actions},
     journal = {Matemati\v{c}eskie zametki},
     pages = {152--155},
     publisher = {mathdoc},
     volume = {51},
     number = {2},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1992_51_2_a22/}
}