1. Naniewicz Z., Hemivariational inequalities with functions fulfilling directional growth condition, Applic. Analysis (to appear).
2. Nonconvex superpotentials in the sense of F. H. Clarke and applications;Panagiotopoulos;Mech. Res. Communs,1981
3. Nonconvex energy functions. Hemivariational inequalities and substationary principles;Panagiotopoulos;Acta Mech.,1983