Proper punctuation in abbreviation of Nota Bene [closed]

Which of the following are "correct" ways to abbreviate Nota Bene?

  • N.B. blahblah
  • n.b. blahblah
  • NB. blahblah
  • nb. blahblah
  • NB: blahblah
  • nb: blahblah
  • NB blahblah
  • nb blahblah
  • (etc.)

Authoritative sources would be much appreciated.


The Chicago Manual of Style says:

NB, n.b. nota bene, take careful note (capitals are illogical but often used for emphasis)

CMS adds that "Latin abbreviations are often set in roman" (i.e. not italic).

I tend to see

NB: The Smiley Police are lurking.

"...whom, n.b., I had never seen."