James, William (1890). The Principles of Psychology. This monumental text can be viewed as the beginning of psychology. Online version
Freud, Sigmund (1900). The Interpretation of Dreams. Dream interpretation became a part of psychoanalysis due to this seminal work. Online version
Freud, Sigmund (1920). Introductory Lectures on Psycho-analysis. Discussion of slips, transference, and dream analysis. Includes classic case studies.