S. Marchi, C-1,C-alpha local regularity for the solutions of the p-laplacian on the Heisenberg group for 2 <= p < 1+root 5, Z ANAL ANWE, 20(3), 2001, pp. 617-636
We prove local Holder continuity of the homogeneous gradient for weak solut
ions u is an element of W-loc(1,p) of the p-Laplacian on the Heisenberg gro
up H-n for 2 less than or equal to p < 1 + <root>5.