NT = New Testament
OT = Old Testament
LXX = Septuagint
Bible books generally abbreviated with first three letters and no period.
Phi = Philippians, not Philemon.
Phm = Philemon
Numbered books will be in the format 1Co = 1 Corinthians. (No Roman numerals).
This will also keep me from having to edit cut-and-paste Bible passages from software, where these abbreviations have become fairly standard.
If this proves to make reading more difficult, let me know, but I figure most people now see these abbreviations so often that spelling the words out has become more of a hindrance than help — and anything that shortens my writing has to be good. Right?