We are often looking for information as we research vintage and historical items and the libraries of various colleges and universities are invaluable. And collectors are often reaching out to us to ask about the origin and dating of certain items.
Specifically, we have found Columbia University's copyright class very useful. And their New York Times Access.
And Cornell Library conservation staff.
And Dartmouth's as well.
Stanford's image of old "Big Game" football programs is the best in the business and a treasure for the collector.
Penn's library also has great history for those interested in athletics.