What if I can't access the original source?
If you are quoting from a secondary source rather than the original source - which should always be used (!) - and the original source is no longer available, both sources must be cited. The original work is cited first, followed by the reference 'quoted from' and the source from which the reference to the original source comes. Here is an example of APA style:
Penrose notes: “it is never resources themselves that are the ‘inputs’ to the production process, but only services that the resources can render” (Penrose, 1959, pp. 24-25, quoted from Vargo & Lusch, 2004, p. 326).