I'm just beginning to read the paper Finding Eisenstein Elements in Cyclic Number Fields of Odd Prime Degree.*
On the third page, in Lemma 2, the author references Proposition 5.11 of David Cox's Primes of the form $x^2+ny^2$, (John Wiley and Sons, New York, 1989), which is apparently found on page 102. It deals with inert primes.
Unfortunately, I don't have access to this book, and it is checked out at my local library for another 3 weeks. Could someone with access perhaps provide the proof of the proposition in question? I'd be very grateful.
*For some reason the link I copy from my browser doesn't seem to work as a link. Googling brings up the paper as the first result though.