“EXISTENCE OF SOLUTIONS OF BOUNDARY VALUE PROBLEMS FOR THE EQUATION $f(t,x,x’,x’’) = 0$ WITH FULLY NONLINEAR BOUNDARY CONDITIONS”, Ann. Sofia Univ. Fac. Math. and Inf., vol. 94, pp. 55–70, Dec. 2002, Accessed: Dec. 14, 2025. [Online]. Available: https://annual.uni-sofia.bg/index.php/fmi/article/view/190