Thomen, H. O. (1973). Supplement to the Index of congressional committee hearings prior to January 3, 1935: Consisting of hearings not catalogued by the U.S. Senate Library, with subject index, shelflist, and bill number index, from the Twenty-fifth Congress, 1839, through the Seventy-third Congress, 1934. Greenwood Press.

Thomen, Harold O. Supplement to the Index of Congressional Committee Hearings Prior to January 3, 1935: Consisting of Hearings Not Catalogued by the U.S. Senate Library, with Subject Index, Shelflist, and Bill Number Index, from the Twenty-fifth Congress, 1839, Through the Seventy-third Congress, 1934. Westport, Conn.: Greenwood Press, 1973.

Thomen, Harold O. Supplement to the Index of Congressional Committee Hearings Prior to January 3, 1935: Consisting of Hearings Not Catalogued by the U.S. Senate Library, with Subject Index, Shelflist, and Bill Number Index, from the Twenty-fifth Congress, 1839, Through the Seventy-third Congress, 1934. Greenwood Press, 1973.