@article{ZNSL_1999_256_a9,
     author = {K. P. Kokhas' and A. Suvorov},
     title = {Spectral estimations for {Laplace} operator for the discrete {Heisenberg} group},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {129--144},
     publisher = {mathdoc},
     volume = {256},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1999_256_a9/}
}