Books on 2-RDM

• Many-electron densities and reduced density matrices edited by Jerzy Cioslowski

  Especially good.

• Density matrices and density functionals. Proceedings of the A. John Coleman Symposium. Edited by R. Erdahl and V. H. Smith, Jr., D. Reidel, Dordrecht, 1987

  Mainly for historical issues.

• Advances in Chemical Physics, Reduced-Density-Matrix Mechanics: With Application to Many-Electron Atoms and Molecules

  Up-to-date infomation on 2-RDM. Historical part is very confusing.