Postprint version. Published in Journal of Integral Equations and Operator Theory, Volume 21, Issue 4, December 1, 1995, pages 383-429. Copyright © 1995 Springer. The original publication is available at http://dx.doi.org/ 10.1007/BF01222016.
NOTE: At the time of publication, the author Mark Stankus was not yet affiliated with Cal Poly.