1. L. F. Thompson, C. G. Willson, and M. A. Bowden,Introduction to Microlithography, 2nd ed., American Chemical Society, Washington, DC (1994).
2. http://courses.nus.edu.sg/course/phyweets/Projects99/Optical/duv_optical_elements.htm.
3. P. Langer, NIST Wafer Flatness Workshop, Personal Communication, (Jan. 30, 2001).
4. http://public.itrs.net/Files/2001ITRS/Home.htm.
5. Interferometric testing of photomask substrate flatness