  We consider a formulation of the algebraic Bethe ansatz for the six vertex
model with non-diagonal open boundaries. Specifically, we study the case where
both left and right $K$-matrices have an upper triangular form. We show that
the main difficulty entailed by those form of the $K$-matrices is the
construction of the excited states. However, it is possible to treat this
problem with aid of an auxiliary transfer matrix and by means of a generalized
creation operator.
