there is a nice paper in the most recent (at least the most recent one to appear on our shelves here in the AOC) issue of ApJ on 183 GHz phase calibration. if you have ADS access, you can find it at: http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001ApJ...553.1036W&db_key=AST&high=3b0028760405556 -bryan