Society of American Historians, McPherson, J. M., & Rubel, D. (2004). "To the best of my ability": The American presidents (Revised US edition.). DK.
Chicago Style (17th ed.) CitationSociety of American Historians, James M. McPherson, and David Rubel. "To the Best of My Ability": The American Presidents. Revised US edition. New York: DK, 2004.
MLA (9th ed.) CitationSociety of American Historians, et al. "To the Best of My Ability": The American Presidents. Revised US edition. DK, 2004.
Warning: These citations may not always be 100% accurate.