By default, Mendeley provides most of the commonly used referencing styles in Mendeley desktop. If you are not able to find the referencing style you required, follow these steps closely:-
If you don't know the name of the style, but know what the final citation should look like, you can use the search by example tool to find styles that most closely match.
Once you've found the style required, click the "Install" button on the search results.
Alternatively, if you are not able to find the style you want, you may edit the style that matches closest to your needs and install the file.
