When writing manuscripts I am often expected to use the three letter abbreviation. The ones listed by Joe Weaks seem to be the standard.
Sorry if I disagree. Publishers, particularly those of journals, do not seem to be able to agree on a common system. Just to give an example: Two of the most reputable journals, the CBQ and the JBL, use different abbreviations. Or look at the Anchor Bible Dictionary. They use "1 Kgdms" for 1 Samuel, but "1 Kgs" for 1 Kings.
Furthermore, Accordance adds to the "mess" when it comes to foreign language resources. For example, in my Zürcher Bible I have to search with the German abbreviations (which, to boot, are idiosyncratic with the ZB), however, the outcome uses English abbreviations in the citations. And furthermore, the navigation drop down box at the bottom of the text window does not work with the ZB, reporting back that "this book does not exist in your bible" or a similar message. All this makes me somewhat unhappy, also leading to the fact that I have to define search limits that I use frequently more than once, depending on the search version I use.
I think this could be simplified: There might be just one type of abbreviation for searching or navigating, but then there should be predefined sets of abbreviations for the output, to be chosen, and maybe even redefined or edited, by the user. This might be achieved by linking to some predefined alias-files.
I do sincerely hope that Accordance gives this some attention in the next release.