I add my thanks too, Mark. Didn't know that was there!
Jeff, you also mentioned the abbreviation "tg," which I don't see in the popup for John 1:18, and could not find in the BW 9 help. I would hazard a guess that it might be the edition of the Greek NT by Samuel Tregelles, one of the great, though now largely forgotten, 19th-century critical editions. BW 9 includes it; in John 1:18 it agrees with B, W-H, and the Nestle/UBS editions against the Byzantine/Majority readings. For more information on this, see (thanks to the BW 9 Help!) http://www.tyndalehouse.com/tregelles/index.html, which notes that Tregelles was a major influence on Westctott and Hort.