The information in citations appears either in the narrative or parentheses:

In the sentence (narrative): According to Kokkinos (2007), burnout is a negative response to stress at work.

Parenthetical: Burnout is a negative response to stress at work (Kokkinos, 2007).

For quotations of a source, the page or paragraph numbers also is included parenthetically:

Quote: Kokkinos (2007) described burnout as "a negative affective response occurring as result of chronic work stress" (p. 2).