Copyright © 1996 Patricia J. Y. Wong and Ravi P. Agarwal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
We shall consider the boundary value problem
are constants satisfying
to characterize the values of
so that it has a positive solution. For the special case
, sufficient conditions
are also established for the existence of positive solutions.