XUPING ZHANG, JINTAO ZHANG, BO YU, EIGENFUNCTION EXPANSION METHOD FOR MULTIPLE SOLUTIONS OF SEMILINEAR ELLIPTIC EQUATIONS WITH POLYNOMIAL NONLINEARITY, SIAM Journal on Numerical Analysis, Vol. 51, No.

E. C. Titchmarsh, Eigenfunction Problems with Periodic Potentials, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 203 ...

Eigenfunction Estimates: Quantitative bounds and asymptotic behaviours that describe the magnitude and concentration phenomena of eigenfunctions of differential operators.