万国著作権条約
After this, he was appointed by Librarian of Congress Archibald MacLeish as head of the Legislative Reference Service and later Chief Assistant Librarian of Congress. After MacLeish resigned, president Harry S. Truman appointed Evans as his successor, a position he held from 1945 to 1953. During his tenure, Evans opposed censorship of the library's holdings, and greatly expanded the library's collection. Well versed in international relations, he also returned a number of manuscripts to their countries of origin. He helped draft the Universal Copyright Convention at Geneva in 1952.