M. J. Cooper (Chapters 1 and 11) Department of Physics, University of Warwick, Coventry CV4 7AL, UK Malcolm Cooper is one of the pioneers of Compton scattering studies of electron momentum density, with many research relevant publications and reviews over four decades. His Warwick research group has been particularly involved in the development of synchrotron-based Compton scattering studies of ferromagnetism, at synchrotron rings in Europe and Japan. Currently he is Head of the Department of Physics at Warwick University. P.E. Mijnarends (Chapter 8) Physics Department, Northeastern University, Boston, Massachusetts 02115 and Interfaculty Reactor Institute, Delft University of Technology, 2629 JB Delft, The Netherlands. Peter Mijnarends has spent most of his research career as an established international leader of positron annihilation studies of solids. He is now a guest scientist at Northeastern University and the Interfaculty Reactor Institute of Delft University of Technology. N. Shiotani (Chapter 3, 9 and 11) Institute of Materials Structure Science, High Energy Accelerator Research Organization Tsukuba 305-0801, Japan. Nobuhiro Shiotani's research has embraced first positron annihilation and latterly Compton scattering methods of studying Fermiology and electron momentum density in a wide range of solids. N. Sakai (Chapter 10) Graduate School and Faculty of Science, Himeji Institute of Technology, Koto, Akou-gun, Hyogo 678-1297, Japan. Nobuhiko Sakai was involved in the very first Compton scattering studies of spin density using cooled beta-emitting polarised sources. Following this breakthrough he has developed synchrotron-based magnetic Compton scattering studies in Japan. His group has been concentrated in finding the change of magnetic electron spin and orbital states in conjunction with crystal structure and phase transitions. A. Bansil (Chapter 8) Professor of Physics, Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA. Arun Bansil leads a group that has led the development and implementation of methodology for carrying out first-principles calculations of spectral intensities relevant to angle-resolved photoemission, positron-annihilation angular correlation spectra and Compton profiles in complex systems, such as the high-Tc's, within the framework of the local density approximation.