  We prove some new results regarding the boundedness, stability and
attractivity of the solutions of a class of initial-boundary-value problems
characterized by a quasi-linear third order equation which may contain
time-dependent coefficients. The class includes equations arising in
Superconductor Theory, and in the Theory of Viscoelastic Materials. In the
proof we use a family of Liapunov functionals W depending on two parameters,
which we adapt to the `error', i.e. to the size of the chosen neighbourhood of
the null solution.
