Anharmonic Oscillator Equations:Treatment Parallel to Mathieu Equation
  The treatment of anharmonic oscillators (including double-wells) by instanton methods is wellknown. The alternative differential equation method is not so wellknown. Here we reformulate the latter completely parallel to the strong coupling case of the cosine potential and Mathieu equation for which extensive literature and monographs exist. 
Jiu--Qing Liang and H.J.W. Mueller--Kirsten