I am having trouble understanding the H NMR for 5-norbornene-2,3-
dicarboxylic anhydride (to see it, please see:
http://www.aist.go.jp/RIODB/SDBS/cgi-bin/direct_frame_top.cgi?lang=eng).
To begin with, I don't understand why H's D and E are labelled as non-