Thanks for the reply. The second paragraph was the most helpful.
This is because I am using Endnote to enter our course readings into our content mangement system (eReserve). eReserve requires the publisher data for copyright reasons.
I have now ensured that the publisher field is in both the reference type and the bibliography template, yet I still have no publisher field after exporting Journal article references from Endnote.
It seems that I am a step closer to a solution, but uncertain on what to do next.