I'm interested in knowing if/how to properly cite a personal communication within a reference and if credit should be given to the primary source (the personal communication), the secondary source (the reference that cites the personal communication), or both.
Hypothetical example: There is a textbook which has tabular data that I would like to reference. The textbook cites the tabular data as being from a personal communication with another author. I see this as a quandary since:
(1) If I reference the textbook without the personal communication, I am not giving proper credit to the original author (even though they never published the data separately in its own right)
(2) If I reference the personal communication, this would be incorrect and perhaps fraudulent as it was not between myself and the author, I am only a third party, and I would not be giving proper credit to the textbook authors, which is how the data was published.
(3) If I reference both, that is somewhat awkward as that would imply that I found the data from both sources independently, even though I only found it in one.
What is the proper way to reference this?