The Complex Lagrangian Germ and the Canonical Operator
  We give a manifestly invariant definition of the Lagrangian complex germ with the minimal degree of accuracy required to define the canonical operator. The equivalence with the traditional definition is proved, and the canonical operator is constructed in new terms. A new form of the quantization condition is given, in which the volume form is assumed to be defined on the universal covering of the Lagrangian manifold rather than on the manifold itself. This allows one to solve a wider class of eigenvalue problems. 
Vladimir Dubnov, Viktor Maslov, Vladimir Nazaikinskii
math-ph math.MP