The most valuable contributions so far have been set down only in private correspondence, and have not as yet been published. (religion-online.org)
We translate private correspondence, web - sites, different research works! (russianwomeninfo.com)
All I see is a second hand report of private correspondence between Dr. Wegman and Dr. Rapp, and nowhere in there do I see a question asked directly to Dr. Bradley. (deepclimate.org)