1. The nature of prejudice;Allport,1954
2. Why survive? Being old in America;Butler,1975
3. “Robert N. Butler, MD (January 21, 1927–July 4, 2010): visionary leader.”;Achenbaum;The Gerontologist,2013
4. “On prejudice.” Sketches and essays;Hazlitt,1903
5. “Tolerance.” Philosophical dictionary,1984