Ry. Ma et al., THE METHOD OF LOWER AND UPPER SOLUTIONS FOR 4TH-ORDER 2-POINT BOUNDARY-VALUE-PROBLEMS, Journal of mathematical analysis and applications, 215(2), 1997, pp. 415-422
In this paper we develop the monotone method in the presence of lower
and upper solutions for the problem u((IV)) = f(x, u(x), u('')(x)), u(
0) = u(1) = u('')(0) = u('')(1) = 0, R --> R is continuous. (C) 1997 A
cademic Press.