1. Über eine frage der eigenwerttheorie;Ambarzumian;Z. Phys. A Hadron. Nucl.,1929
2. On the uniqueness of the solution of the problem of electromagnetic sounding;Tikhonov;Dokl. Akad. Nauk SSSR,1949
3. The Inverse Sturm-Liouville Problem;Levinson;Mat. Tidsskr. B,1949
4. Sturm-Liouville Operators and Their Applications;Marčenko,1986
5. Inverse Sturm-Liouville Problems;Levitan,1987