Integrable Kondo impurities in two cases of the one-dimensional t-J model a
re studied by means of the boundary Z(2)-graded quantum inverse scattering
method. The boundary K-matrices depending on the local magnetic moments of
the impurities are presented as non-trivial realizations of the reflection
equation algebras in an impurity Hilbert space. Furthermore, these models a
re solved by using the algebraic Bethe ansatz method and the Bethe ansatz e
quations are obtained. (C) 1999 Elsevier Science B.V.