http://www.fzt.haw-hamburg.de/pers/S...5-122Paper.pdf
Sadly this paper does slip up a little inasmuch as the authors have gone for the formulae and skipped the authors' caveats.
Hoppy alludes to other factors which will include wing sweep, airfoil characteristics, thickness/chord ratio. In the paper I allude to please note that the analysis is entirely empirical. Alas that is where these empiricists themselves went a bit wrong. They thought everyone else was using the same empiricism!
Try Stanford Uni for Shevell's program on compressibility, Mdd, Mcrit. I seem to recall his work was based on conventional aircraft but without the tail in a wind tunnel. He made an allowance for tail down force, which no small matter the paper reviewers missed in their haste to grab the formulae. Tisk Tisk.
Lumme its all a long time ago now.
Hope this is helpful and gives you are sources to search for.
The "E"