In-Text References Using APA Style In Academic Writing
The documentation style of the American Psychological Association (APA) is used by many different kinds of scholars and it is certainly a very effective system for citing and listing sources. However, it is not the easiest of referencing methods to implement, so some notes on how to add in-text citations to your document using APA style as outlined in the 6th edition of the association’s Publication Manual may prove helpful.

In-text citations in APA style are parenthetical author–date references, so they generally appear in parentheses and include the last name of the author and the date of publication, as in (Smith, 2008). Alternatively, either or both elements can appear in the main text: ‘Smith’s study (2008) shows’ or ‘A study done in 2008 (Smith) shows’ or ‘Smith’s 2008 study shows.’ The key is to ensure that you always include both a correctly spelled author name and an accurate publication date.

Two authors are treated exactly the same as one, so (Smith & Johnson, 2009), ‘Smith and Johnson’s study (2009) shows,’ ‘A study conducted in 2009 (Smith & Johnson) shows’ and ‘Smith and Johnson’s 2009 study shows’ are all correct. Do notice, however, that an ampersand (&) is used between the author names when they appear parenthetically, but the word ‘and’ is the right choice when the author names appear in the main text.

When a source has three or more authors the procedure becomes more complicated. For a source with three to five authors, all authors should be listed for the first citation of the source, whether those names appear in parentheses or the main text: (Smith, Jones, & Johnson, 2010), ‘The study by Smith, Jones, and Johnson (2010) demonstrates’ and so on. After the first citation of such a source, however, only the first author’s name should be used for all subsequent in-text references in a document, and that name should be followed by ‘et al.,’ an abbreviation that means ‘and others’ and closes with a full stop in APA style. Later citations of the Smith, Jones, and Johnson source would therefore appear as (Smith et al., 2010), ‘The 2010 study by Smith et al. shows’ and so on. This means that special care is required to keep track of first versus subsequent citations and ensure that each citation appears in the correct format.

For a source with six or more authors, the procedure is easier because only the first author’s name is used regardless of whether it appears in a first or a subsequent citation of the source. In every instance that name is followed by ‘et al.’ Therefore, an article written in 2011 by Smith, Jones, Johnson, Wilson, Power, and Barnes would appear consistently in all in-text citations as (Smith et al., 2011), with ‘Smith et al. showed in 2011 that,’ ‘The study by Smith et al. (2011) showed’ and other possibilities using that basic formula all being correct.

You may have already realised that there is a possibility for confusion using this style if two or more sources each with three or more authors shorten to the same form. For example, a study written by Smith, Jones, Johnson, and Wilson in 2012 would shorten to (Smith et al., 2012), but so would a study published in 2012 by Smith, Jones, Wilson, and Johnson. These sources should therefore be distinguished in shortened forms by adding as many of the subsequent author names for each source as necessary to avoid confusion. The first study would therefore appear as (Smith, Jones, Johnson, et al., 2012), while the second would be correct as (Smith, Jones, Wilson, et al., 2012). Do note that although there is no comma preceding ‘et al.’ in normal shortened references containing one author name, a comma is used before the abbreviation in these longer shortened references.