1. V. Janiš
    Free-energy functional in the generalized coherent- potential approximation
    Phys. Rev. B 40 (1989) 11331
  2. V. Janiš
    $U=\infty$ Hubbard model: Towards the exact solution in $d=\infty$
    International Journal of Modern Physics B 3 (1989) 2149-2157.