  The time-dependent variational principle for many-body trial states is used
to discuss the relation between the approaches of different molecular dynamics
models to describe indistinguishable fermions. Early attempts to include
effects of the Pauli principle by means of nonlocal potentials as well as more
recent models which work with antisymmetrized many-body states are reviewed
under these premises.
  Keywords: Many-body theory; Fermion system; Molecular dynamics; Wave-packet
dynamics; Time-dependent variational principle; Statistical properties;
Canonical ensemble; Ergodicity; Time averaging
