  Local boundedness and Harnack inequalities are studied for solutions to
parabolic and elliptic integro-differential equations whose governing nonlocal
operators are associated with nonsymmetric forms. We present two independent
proofs, one being based on the De Giorgi iteration and the other one on the
Moser iteration technique. This article is a continuation of a recent work by
the same authors, where H\"older regularity and a weak Harnack inequality are
proved in a similar setup.
