  Three kinds of integrable Kondo problems in one-dimensional extended Hubbard
models are studied by means of the boundary graded quantum inverse scattering
method. The boundary K matrices depending on the local moments of the
impurities are presented as a nontrivial realization of the graded reflection
equation algebras acting in a $(2 s_\alpha+1)$-dimensional impurity Hilbert
space. Further, these models are solved using the algebraic Bethe ansatz method
and the Bethe ansatz equations are obtained.
