On Duru-Kleinert Path Integral In Quantum Cosmology
  We show that the Duru-Kleinert fixed energy amplitude leads to the path integral for the propagation amplitude in the closed FRW quantum cosmology with scale factor as one degree of freedom. Then, using the Duru-Kleinert equivalence of corresponding actions, we calculate the tunneling rate, with exact prefactor, through the dilute-instanton approximation to first order in \hbar. 
M. A. Jafarizadeh, F. Darabi, A. R. Rastegar