In the Reed and Simon book, Appendix X.7, they mention that Friedrichs provided the first examples of inequivalent representations of the canonical commutation relations via the Weyl relations in the late 1940s. However, the series of papers by K.O. Friedrichs that I found seem to be from the 1950s, they are "Mathematical aspects of the quantum theory of fields", and I am not sure at all if any example is there.

Could anyone provide a precise reference (including chapter or section, if possible) where I can find Friedrichs' examples of inequivalent representations?

Thanks in advance.