Dr. Alok Kumar,. 2024. “SPECTRAL THEORY OF EIGENFUNCTION EXPANSION WITH SECOND ORDER DIFFERENTIAL EQUATION”. Journal of Validation Technology, ISSN: 1079-6630, E-I SSN: 2150-7090 UGC CARE II 30 (1):66-74. https://doi.org/10.1080/jvtnetwork.v30i1.59.