has been in the of a Symmetry major ingredient development quantum perturba tion and it is a basic of the of theory, ingredient Theory integrable (Hamiltonian and of the the use in context of non Hamiltonian) systems;. has been in the of a Symmetry major ingredient development quantum perturba tion and it is a basic of the of theory, ingredient Theory integrable (Hamiltonian and of the the use in context of non Hamiltonian) systems;