  We derive local boundedness estimates for weak solutions of a large class of
second order quasilinear equations. The structural assumptions imposed on an
equation in the class allow vanishing of the quadratic form associated with its
principal part and require no smoothness of its coefficients. The class
includes second order linear elliptic equations as studied by D. Gilbarg and N.
S. Trudinger [1998] and second order subelliptic linear equations as studied by
E. Sawyer and R. L. Wheeden [2006 and 2010]. Our results also extend ones
obtained by J. Serrin [1964] concerning local boundedness of weak solutions of
quasilinear elliptic equations.
