In academic texts, writers usually use 3 steps to present a citation.
The steps are:
(1) Signal: Show the reader that you are going to give a citation.
(2) Citation: Give the quote or mention the examples.
(3) Explanation: Say why you used the citation, or what it means.
Here is an example:
Professor Nation's main argument states (signal) that students should study high-frequency academic vocabulary (citation). This means that students should first focus on words that often appear in academic texts (explanation).
Look at the four citations in the table below. Only one citation has all three steps described above. The other examples in the table are all missing one of the steps.
Read each citation in the table. Then decide which of the 3 steps is missing.