The paper presents a box scheme with quadratic basis functions for the
discretisation of elliptic boundary value problems. The resulting dis
cretisation matrix is non-symmetrical (and also not an M-matrix). The
stability analysis is based on an elementwise estimation of the scalar
product [A(h) u(h), u(h)]. Sufficient conditions placed on the triang
les of the triangulation lead to discrete ellipticity. Proof of an O(h
(2)) error estimate is given for these conditions.