When you want to use a quote but can’t access the original source, you can cite it indirectly. In the in-text citation, first mention the source you want to refer to, and then the source in which you found it. For example:
Smith (1995, cited in Davies, 2005) divides the process into four steps…
It’s advisable to avoid indirect citations wherever possible, because they suggest you don’t have full knowledge of the sources you’re citing. Only use an indirect citation if you can’t reasonably gain access to the original source.