The number of sources you cite in your paper depends on the purpose of your work. For most papers, cite one or two of the most representative sources for each key point. Literature review papers, however, typically include a more exhaustive list of references.
Provide appropriate credit to the source (e.g., by using an in-text citation) whenever you do the following:
- paraphrase (i.e., state in your own words) the ideas of others
- directly quote the words of others
- refer to data or data sets
- reprint or adapt a table or figure, even images from the internet that are free or licensed in the Creative Commons
- reprint a long text passage or commercially copyrighted test item
Determining the appropriate level of citation is covered in Section 8.1 of the APA Publication Manual, Seventh Edition
This guidance is the same as in the 6th edition.
Avoid both undercitation and overcitation. Undercitation can lead to plagiarism and/or self-plagiarism. Overcitation can be distracting and is unnecessary.
For example, it is considered overcitation to repeat the same citation in every sentence when the source and topic have not changed. Instead, when paraphrasing a key point in more than one sentence within a paragraph, cite the source in the first sentence in which it is relevant and do not repeat the citation in subsequent sentences as long as the source remains clear and unchanged.
Figure 8.1 in Chapter 8 of the Publication Manual provides an example of an appropriate level of citation.