The use of 'et al' in citations and bibliographies is a practice which varies from style to style, and there are a number of conditional arguments which can be applied to its use.
An example of this type of logic would be to say 'if a reference has three or fewer authors, display all of the author names in full. If a reference has four or more authors, display the first author and add 'et al' to reflect the additional authors'.
The threshold that triggers this behaviour can be modified by editing the style using the CSL Editor - and you can find step-by-step instructions on how to modify this behaviour below.
For this example, we'll be using the American Psychological Association (APA) (6th edition) style and we'll be modifying how 'et al' is used in in-line citations.
1. Firstly, we need to open the APA style for editing using the CSL Editor. You can find the steps for this in the first section of this guide - an overview of the CSL Editor.
2. Once the style has been opened for editing, we need to identify the element that we want to update. In this instance, we know we want to modify the in-line citations, so we can find those in the Example Panel.
3. From the example citations that are provided, we can see that 'et al' is already being used for in-line citations. Assuming we want to modify this behaviour, we need to modify the settings associated with In-line citations. Click on the 'In-line Citations' heading in the Style Overview panel to display the settings for this item.
4. With In-line citations selected, we can see a number of settings that control the use of 'et al'. In this instance, the relevant fields are 'et-al-min' (set to 6), et-al-use-first (set to 1), et-al-subsequent-min (set to 3) and et-al-subsequent-use-first (set to 1).
In lay terms, this can be read as follows:
If a reference has five or fewer authors, display all the author names in the citation. If a reference has six or more authors, display the first name followed by 'et al' in the citation.
If a reference has three or more authors, display all three authors in the first citation, but for any subsequent citations use the first name, followed by 'et al'.
4. If we want to modify this behaviour, we just need to alter the values set here. As an example, let's look at how to cause the style to display the first three names before displaying 'et al'. To achieve this, we just need to modify the setting for 'et-al-use-first' to be '3' instead of '1'.
5. As soon as this value is changed, you should see the change take place in the example panel, with three names being displayed (followed by et al) instead of one.
6. However, note that the rules which apply to subsequent citations will still apply, so any citations of a reference with three or more authors - other than the very first - will use the first name followed by 'et al'. We can either modify 'et-al-subsequent-use-first' to be '3' to bring it into line with 'et-al-use-first' (modified in step 4), or we can remove the instructions for 'subsequent citations entirely by settings both the relevant values to be blank. This will mean that all citations are subject to the same rules, without considering if they're the first or a subsequent instance.
The style has now been modified as intended. To start using it in your working documents, see the section on saving and installing your modified style.