  Quasi-achromat lattices (small dispersion is allowed in their straight
sections, between their cells) are considered; in a cell, there are bending
magnets of two kinds, of unequal magnetic field. Minimization of the effective
emittance is carried out by the following algorithm (which follows Teng, and
partly Lee).
  (1) Every inner dipole's contribution to the natural emittance is minimized
with respect to all optics parameters (relating to dispersion and
beta-function), except for the shift parameter, s_0, which specifies the
interval between the beta-function minimum and the center of a magnet; for a
side bending magnet, its contribution to an integral relating to the effective
emittance (the relation uses the fact that the arithmetic mean majorizes the
geometric mean) is minimized.
  (2) The other parameters of dipoles (fields, lengths or angles ratios,
shifts) are restricted with the boundary conditions: the equality of
Courant-Snyder invariants on the exit from a magnet and on the entrance to the
following one. (3) The minimum of effective emittance and the last free
parameters (two or three) can be found by computation.
  The accuracy of this method falls with decreasing of the number of internal
dipoles in a cell, and still the isomagnetic Tanaka-Ando minimum (for the
modified DBA*-lattice which has no inner dipoles) is reproduced with accuracy
better than half a percent. If the number of dipoles per cell does not exceed
four, the smallest effective emittance (14% lower than TA-limit) is achieved
for QBA**-lattice where all dipoles have nonzero shifts.
