I'm an undergraduate writing a paper for a philosophy course in logic. My paper is exploring a relationship between Leibniz' logic and graph theory. In writing the paper, I've found some material in Leibniz' work on combinatorics that (to me) strongly resembles graph theory. However, I can't find anything that seriously discusses Leibniz in relation to the history of graph theory --- everything seems to start with Euler. (Most read "Leibniz made early contributions to topology. Later on, Euler developed graph theory" and continue onward from there)
I'd like to be able to say "I looked around on Google scholar, etc, and I couldn't find anything about this topic" by way of suggesting "It's possible that the midterm paper that you're reading is bumping up against an original area of research."
What kind of evidence is appropriate in this situation? Would providing something like the number of results of a search on Google scholar be worthwhile? In general, is there a technique to demonstrate the absence of literature about a certain topic?