A concise discussion of Hartree-Fock in Nuclear Physics can be found in "The Nuclear Many-Body Problem" by P. Ring and P. Schuck (Springer, 1980).
A very detailed, recent derivation is given in "From Nucleons to Nucleus. Concepts of Microscopic Nuclear Theory" by J. Suhonen (Springer, 2007). The latter might be available electronically if your university has a subscription to SpringerLink.
As for the "density matrix approximation" - do you mean Density Matrix Expansion (DME)? In this case, have a look at the original papers by Negele and Vautherin: Phys. Rev. C 5, 1472 (1972), and to the prequel PRC 1, 1260 (1970). Clicking "Citing Articles" on the Phys. Rev. web site gives suggestions to more recent applications and modifications.