New York Times Company Records. Adolph S. Ochs Papers. Manuscripts and Archives Division, The New York Public Library. Finding Aid.
Omaha Tribüne. Nebraska State Historical Society .
Oral History Collection of the Research Foundation for Jewish Immigration. Leo Baeck Institute, New York, NY. Finding aid.
Oral History interview with George Bowman. #89OH79, Hershey Community Archives Oral History Collection. Available online.
Origin, Growth, and Usefulness of the Chicago Board of Trade: Its Leading Members, and Representative Businessmen in Other Branches of Trade . New York, Historical Publishing Co, 1885.
Otto L. Bettmann Personal Papers Collection, 1976-1998. Special Collections; Florida Atlantic University Libraries, Boca Raton, Florida. Finding aid.
Pabst Brewing Company Collection. Milwaukee County Historical Society. Finding aid.
Pabst Brewing Company, Records (1873-197?). University of Wisconsin-Milwaukee Libraries, Archives Department. Finding aid.
Partners: A History of the Development of the Wyomissing Industries. Reading: The Wyomissing Industries, 1936.
Philipp Brothers Collection; AR 25131. Leo Baeck Institute, New York. Finding aid.
Potthast Brothers Collection, PP7. Maryland Historical Society Library, Special Collections Department. Finding aid.
Potthast Brothers, Inc. 1892-1975, Correspondence, 1933-34, n.d. Maryland Historical Society Library, Special Collections Department.
Potthast Brothers, Inc. 1892-1975, Letterbooks, 1908-32. Maryland Historical Society Library, Special Collections Department.
R.G. Dun & Co. / Dun & Bradstreet Collection. Baker Library, Harvard Business School. Finding aid.
Rath Packing Company Records, 1890-1985, MS 562. Special Collections Department, Iowa State University Library. Finding aid.
Records of B. Altman & Co. 1876-1955. The New-York Historical Society. Finding Aid.
Reminiscences of Gerard Swope, Interview by Harlan B. Phillips, 1955. Oral History Collection, Columbia University, New York, NY. Online catalog.
Roebling Collection, 1830-1926. Rensselaer Polytechnic Institute, Archives & Special Collections, Troy, New York. Finding aid.
Roebling Family Papers, 1821-1960. Special Collections and University Archives Rutgers, The State University of New Jersey, New Brunswick, NJ. Finding aid.
Rothschild Archive. London, United Kingdom. Finding aid.