  In an interesting note, E.M. Stein observed some 20 years ago that while the
Kohn Laplacian $\square_b$ on functions is neither locally solvable nor
(analytic) hypoelliptic, the addition of a non-zero complex constant reversed
these conclusions at least on the Heisenberg group, and Kwon reproved and
generalized this result using the method of concatenations. Recently Hanges and
Cordaro have studied this situation on the Heisenberg group in detail. Here we
give a purely $L^2$ proof of Stein's result using the author's now classical
construction of $(T^p)_\phi = \phi T^p +...,$ where $T$ is the 'missing
direction' on the Heisenberg group.
