 While the extensive book collection, with more than 9500 entries, can be searched by use of an online catalogue, the institute also owns more than a hundred microfilm collections and digital resources.These include, among others, copies of the papers of President Theodore Roosevelt; the presidential Office Files of Franklin D. Roosevelt, Harry S. Truman, Dwight D. Eisenhower, and John F. Kennedy; the papers of W.E.B.Du Bois; and Dutch-American diplomatic correspondence (dating back to 1784).