Secondary Referencing
Secondary Referencing is when an author quotes the work of another. When this happens, you need to either find the original source of the work or use secondary referencing to cite and reference it.
Example
Imagine you have read a book by Mearns and Cooper (2018) and on page 56 it cites a piece of work by Rogers (1957) and has the full reference to it in the reference list. You cannot locate the original work by Rogers so what do you do?
In text:
(Rogers, 1957, cited in Mearns and Cooper, 2018, p. 56)
or
Rogers (1957, cited in Mearns and Cooper, 2018, p. 56) argued that...
In your reference list or bibliography:
Mearns, D. and Cooper, M. (2018) Working at Relationship Depth in Counselling and Psychotherapy. 2nd edn. London: Sage Publications.