  We study the Kondo effect of a quantum dot placed in a complex mesoscopic
structure. Assuming that electronic interactions are taking place solely on the
dot, and focusing on the infinite Hubbard interaction limit, we use a
decoupling scheme to obtain an explicit analytic approximate expression for the
dot Green function, which fulfills certain Fermi-liquid relations at zero
temperature. The details of the complex structure enter into this expression
only via the self-energy for the non-interacting case. The effectiveness of the
expression is demonstrated for the single impurity Anderson model and for the
T-shaped network.
