Professional and personal files including Armstrong's correspondence with professional associations, other engineers, and friends, his research notes, circuit diagrams, lectures, articles, legal papers, and other related materials. Of his many inventions and developments, the most important are: 1) the regenerative or feedback circuit, 1912, the first amplified radio reception, 2) the superheterodyne circuit, 1918, the basis of modern radio and radar, 3) superregeneration, 1922, a very simple, high-power receiver now used in emergency mobile service, and 4) frequency modulation - FM, 1933, static-free radio reception of high fidelity. More than half the files concern his many lawsuits, primarily with Radio Corporation of America, over infringement of the Armstrong patents. Litigation continued until 1967. Other files deal with his work in the Marcellus Hartley Research Laboratory at Columbia University, 1913-1935, and with the American Expeditionary Forces in France during World War I, his Air Force contracts for communications development, Army research during World War II, the Radio Club of America, the Institute of Radio Engineers, FM development at his radio station at Alpine, N.J., the use of FM in television, his involvement in Federal Communications Commission hearings and legislation, and his work with the Zenith Radio Corporation. Also, letters to H.J. Round

Correspondence, manuscripts, lectures, notes, diaries, notebooks, reports, financial records, blueprints, photographs, and printed materials of Y.C. James Yen and the IIRR concerned with the development, sharing, and financing innovative methods of teaching, improving agriculture, health and family planning, and education in impoverished villages. Among the cataloged correspondents are: Pearl Buck, William O. Douglas, Nelson Rockefeller, and DeWitt Clinton.

The correspondence, research, and teaching files of French-American cultural historian and Columbia University professor emeritus Jacques Barzun (1907-2012).

Correspondence, manuscripts, notes, documents, book typescripts, photographs, and printed materials covering the time from Dorfman's early interest, as a graduate student, in the economic thought of Thorstein Veblen until his retirement. There is correspondence with his academic colleagues, students, publishers, and the family and students of Thorstein Veblen, as well as manuscripts, typescripts, drafts, revisions, notes, photographs, pamphlets, and related materials for his articles and books which include: THORSTEIN VEBLEN AND HIS AMERICA, 1934; THE ECONOMIC MIND IN AMERICAN CIVILIZATION, 1946-1959; EARLY AMERICAN POLICY, 1960; INSTITUTIONAL ECONOMICS, 1963; TYPES OF ECONOMIC THEORY, 1967; and NEW LIGHT ON VEBLEN, 1973