1. R. S. Chisholm, W. N. Everitt and L. L. Littlejohn, An integral operator inequality with applications, J. Inequal. Appl. 3 (1999), 245–266.
2. Jyoti Das, W. N. Everitt, D. B. Hinton, L. L. Littlejohn and C. Markett, The fourth-order Bessel-type differential equation, Appl. Anal. 83 (2004), 325–362.
3. W. N. Everitt, Fourth-order Bessel-type special functions: a survey, submitted to World Scientific for the proceedings of the conference held at the Technical University, Munich; July 2005.
4. W. N. Everitt and H. Kalf, The Bessel differential equation and the Hankel transform, to appear in J. Comput. Appl. Math.
5. W. N. Everitt, H. Kalf, L. L. Littlejohn and C. Markett, Additional spectral properties of the fourth-order Bessel-type differential equation, Math. Nachr. 278 (2005), 1538–1549