@article{MZM_1992_51_5_a20,
     author = {S. I. Piskarev},
     title = {Compactness properties in the theory of the cosine operator functions},
     journal = {Matemati\v{c}eskie zametki},
     pages = {151--153},
     publisher = {mathdoc},
     volume = {51},
     number = {5},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1992_51_5_a20/}
}