**an asymmetric version of perturbation****method****assumes that**

**a Hamiltonian H = H(g), g~0 of physical interest is****weakly parameter-dependent****"too distant" from any easily diagonalized model**

**tridiagonal (e.g., represented in a Lanczos bi-orthogonal basis)**

**recent****proceedings****may be also consulted for****detailed account****of the****highly schematic V(x) = polynomial(x)/polynomial(x) .**