Canonical path integral quantization of the finite dimensional systems   with constraints
  The path integral formulation of constrained systems leads to obtain the equations of motion as total differential equations in many variables. If these equations are integrable then one can constuct a valid and a canonical phase space coordinates. The path integral is obtained as an integration over the canonical phase space coordinates. This approach is applied to obtain the path integral for three singular systems and it is shown that in our formulation there is no need to distinguish between first and second-class constraints, no need for fixing any gauge, as will as no need to enlarge the phase space. 
Sami I. Muslih