Both Appelton and Crouse Hines publish bookelets called Code Digest that explaine very well the "how tos" and "whys" of conduit and conduit fittings in classified areas. You can get them free from you local rep. They are very good with clear explainations and excellant drawings. They are as I said free but if you had to pay for them you could not complain.
Appelton is located at:
you can sigh up for theri bookelt on their website. If you doing much work in classified area you need their catalogues ans well as an OZ Gedney catalogue.