1. Contact Lenses;Phillips,1989
2. Computer programs;Douthwaite,1987
3. eg. Contact lens analysis software, Hough, D.A. Telephone 0480-475742.
4. Contact lenses. Part 1. Specification for rigid corneal and scleral contact lenses,1992
5. The development of the back surface design of rigid lenses;Atkinson;Contax,1987