  Signatures of quadratic forms have been generalized to hermitian forms over
algebras with involution. In the literature this is done via Morita theory,
which causes sign ambiguities in certain cases. In this paper, a hermitian
version of the Knebusch Trace Formula is established and used as a main tool to
resolve these ambiguities.
  The last page is an erratum for the published version. We inadvertently (I)
gave an incorrect definition of adjoint involutions; (II) omitted dealing with
the case $(H\times H, \widehat{\phantom{m}}\,)$. As $W(H\times H,
\widehat{\phantom{m}}\,)= W(R\times R, \widehat{\phantom{m}}\,)=0$, the
omission does not affect our reasoning or our results. For the sake of
completeness we point out where some small changes should be made in the
published version.
