IBM Archives: Frequently Asked Questions(PDF). [2014-03-31]. （原始内容存档(PDF)于2018-11-06）. Some accounts of the merger forming CTR state that three corporations were merged. This reference notes that only three of the four merged corporations are represented in the CTR name. That may be the reason for the differing accounts.
O'Connor, J.J.; Robertson, E.F. Herman Hollerith. The MacTutor History of Mathematics Archive. School of Mathematics and Statistics, University of St Andrews, Scotland. [5 March 2013]. （原始内容存档于2019-04-08）.引文使用过时参数coauthors (帮助)
Da Cruz, Frank. Herman Hollerith. www.columbia.edu. Columbia University. 28 Mar 2011 [28 Feb 2014]. （原始内容存档于2011-05-13）.
O'Connor, J.J.; Robertson, E.F. Herman Hollerith. The MacTutor History of Mathematics Archive. School of Mathematics and Statistics, University of St Andrews, Scotland. [5 March 2013]. （原始内容存档于2019-04-08）.引文使用过时参数coauthors (帮助)
IBM Archives: Frequently Asked Questions(PDF). [2014-03-31]. （原始内容存档(PDF)于2018-11-06）. Some accounts of the merger forming CTR state that three corporations were merged. This reference notes that only three of the four merged corporations are represented in the CTR name. That may be the reason for the differing accounts.
