The INC model lacks justification for nucleon energies (inside the nucleus) below around 100-150 MeV. Pre-equilibrium models [85, 97-99] have been used for some time in nuclear physics in this energy domain. These models follow a population of quasi-particle excitations of the nuclear Fermi gas by means of a master equation. Quasi-particle states are characterized by their particle escape and damping widths. Angular distributions are asso­ciated with the escaping particles. In a sense, pre-equilibrium models allow an easier phenomenological adjustment of angular distributions than does the intranuclear cascade. There are many versions of pre-equilibrium models, but unhappily no clear criteria to choose among them, except their ability to reproduce experimental data.