  We turn back to some pioneering results concerning, in particular, nonlinear
potential theory and non-homogeneous boundary value problems for the so called
p-Laplacian operator. Unfortunately these results, obtained at the very
beginning of the seventies, were kept in the shade. We believe that our proofs
are still of interest, in particular due to their extreme simplicity. Moreover,
some contributions seem to improve the results quoted in the current
literature.
