1. A review of the electron beam techniques is given by C. J. Varker (in this volume).
2. Photoelectron Spectroscopy for the Examination of Surfaces and Interfaces is reviewed by W. E. Spicer (in this volume).
3. R. Williams in Semiconductors and Semimetals, 6, 97 ( R. K. Willardson, Ed. ), Academic (1970).
4. R. Williams and R. H. Bube, J. Appl. Phys. 31, 968 (1960).
5. R. Williams, Phys. Rev. 140, A569 (1965).