1. R. P. Agarwal, D. O’Regan and P. J. Y. Wong, Positive Solutions of Differential, Difference and Integral Equations, Kluwer, Dordrecht, 1999.
2. R. P. Agarwal, D. O’Regan and P. J. Y. Wong, Constant-sign solutions of a system of Fredholm integral equations, Acta Applicandae Mathematicae 80(2004), 57–94.
3. R. P. Agarwal, D. O’Regan and P. J. Y. Wong, Eigenvalues of a system of Fredholm integral equations, Math. Comput. Modelling, to appear.
4. R. P. Agarwal, D. O’Regan and P. J. Y. Wong, Triple solutions of constant sign for a system of Fredholm integral equations, Cubo Matematica Educacional, to appear.
5. R. P. Agarwal, D. O’Regan and P. J. Y. Wong, Constant-sign solutions of a system of integral equations: The semipositone and singular case, preprint.