Existence of solutions to first-order singular and nonsingular initial value problems. Kelevedjiev, Petio S. — 2008 Electronic Journal of Differential Equations (EJDE) [electronic only]
Minimal and maximal solutions for two-point boundary-value problems. Grammatikopoulos, Myron K.; Kelevedjiev, Petio S. — 2003 Electronic Journal of Differential Equations (EJDE) [electronic only]
Another understanding of fourth-order four-point boundary-value problems. Kelevedjiev, Petio S.; Palamides, Panos K.; Popivanov, Nedyu — 2008 Electronic Journal of Differential Equations (EJDE) [electronic only]