“…Hald [2][3][4]. Several works improved their methods and extended them to other problems and different boundary conditions [5][6][7][8][9][10], the quasilinear p-Laplacian operator [11,12], differential pencils [13,14], eigenvalue depending coefficients or boundary conditions [15,16], and also to quantum graphs [17][18][19][20][21][22][23]. However, most of these works assume the existence of a formula for the asymptotic behavior of eigenvalues or developed it using transmutation operators and Prufer's type transformations.…”