The Klein-Gordon oscillator and the proper time formalism in a Rigged   Hilbert sapace
  The implications of manifestly covariant formulation of relativistic quantum mechanics depending on a scalar evolution parameter, canonically conjugated to the variable mass, is still an unsettled issue. In this work we find a complete set of generalized eigenfunctions of the Klein-Gordon Oscillator in the above mentioned formulation, in the Rigged Hilbert Space with Tempered Ultradistributions. We briefly comment on some models where this solution could be applied. 
A. G. Grunfeld and M. C. Rocca