  Kato's second representation theorem is generalized to solvable sesquilinear
forms. These forms need not be non-negative nor symmetric. The representation
considered holds for a subclass of solvable forms (called hyper-solvable),
precisely for those whose domain is exactly the domain of the square root of
the modulus of the associated operator. This condition always holds for closed
semibounded forms, and it is also considered by several authors for symmetric
sign-indefinite forms. As a consequence, a one-to-one correspondence between
hyper-solvable forms and operators, which generalizes those already known, is
established.
