@article{SM_1973_21_4_a6,
     author = {V. N. Tulovskii and M. A. Shubin},
     title = {On~asymptotic distribution of eigenvalues of pseudodifferential operators in~$\mathbf R^n$},
     journal = {Sbornik. Mathematics},
     pages = {565--583},
     publisher = {mathdoc},
     volume = {21},
     number = {4},
     year = {1973},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1973_21_4_a6/}
}