In this volume, the authors extend the calculus of finite differences to Dirac's equation. They obtain solutions for particles with negative mass that are completely equivalent to the solutions with positive mass. In addition, they obtain solutions for nuclear distances of the order of 10-13m and less rather than for the usual atomic distances. They report a number of other deviations from the differential theory, for instance they found a slight deviation in the eigenvalues of an electron in a Coulomb field, similar to the Lamb shift. In two sections some surprising results are shown for the concept of space caused by the replacement of dx by delta x.

1. Introduction
2. Modified Dirac Equation
3. Inhomogeneous Dirac Difference Equation
4. Dirac Difference Equation in Spherical Coordinates
5. Inhomogeneous Equations for Coulomb Potential
6. Appendix
References and Bibliography
Index