Semiclassical Analysis of Quasi-Exact Solvability
  Higher-order WKB methods are used to investigate the border between the solvable and insolvable portions of the spectrum of quasi-exactly solvable quantum-mechanical potentials. The analysis reveals scaling and factorization properties that are central to quasi-exact solvability. These two properties define a new class of semiclassically quasi-exactly solvable potentials. 
C. M. Bender (Washington U.), G. Dunne (U. Connecticut) and M. Moshe   (Technion)