  We present new equilibrium component distribution functions that depend on
three analytic integrals in a Stackel potential, and that can be used to model
stellar discs of galaxies. These components are generalizations of two-integral
ones and can thus provide thin discs in the two-integral approximation. Their
most important properties are the partly analytical expression for their
moments, the disc-like features of their configuration space densities
(exponential decline in the galactic plane and finite extent in the vertical
direction) and the anisotropy of their velocity dispersions. We further show
that a linear combination of such components can fit a van der Kruit disc.
