Don't forget to ask the librarians, they may know where to look, and if they don't they may search with you, which will give you an idea of how you should be searching too. This could be important for your future research as if they are like the ones here they will try to get to know your area, where the best sources are, and may even send you notes about something they have found. Also, remember to read journal stuff around the periphery of your area too, as sometimes they will touch on your own stuff, or have references worth looking up.