On the asymptotic distribution of eigenvalues for semi-elliptic operators
Akira Tsutsumi, Chung Lie Wang · Transactions of the American Mathematical Society · 1974
This paper is focused on the asymptotic distribution of eigenvalues for semielliptic operators under weaker smoothness assumptions on coefficients of operators than those of F. E. Browder [3] and Y. Kannai [8] by applying the method of Maruo-Tanabe [9].