Charles Francis Adams, "The Era of Change," in Charles F. Adams and Henry Adams, Chapters of Erie and Other Essays (Boston: James Osgood, 1871; reprint, New York: Augustus M. Kelley, 1967), 365.
Joseph Nimmo Jr., Railroad Federations and the Relation of the Railroads to Commerce . . . (Washington, D.C.: GPO, 1885), 8.
"Report of the Auditor of Railroad Accounts," 46th Cong., 2d sess., 1911, H. Ex. Doc. 1, 17-18.
The best of these are by Maury Klein; see esp. Klein, Union Pacific
Maury Klein, Union Pacific, (Garden City, N.Y.: Doubleday, 1987).