  Local unitary invariance and the notion of negativity fonts are used as the
principle tools to construct four qubit invariants of degree 8, 12, and 24. A
degree 8 polynomial invariant that is non-zero on pure four qubit states with
four-body correlations and zero on all other states, is identified.
Classification of four qubit states into seven major classes, using criterion
based on the nature of correlations, is discussed.
