Harper & Row v. Nation Enterprises, 471 U.S. 539 (1985).
(Harper v. Nation, 1985)
Most court decision APA citations have three basic elements:
Harper & Row v. Nation Enterprises,
471 U.S. 539
(E.D. Wis. 1972).
*Omit the name of the Supreme Court and its jurisdiction in references to the Supreme Court Reporter (S. Ct.) and United States Reports (U.S.). Likewise, omit the court’s name and its jurisdiction if (a) the deciding court is the highest court of a state or (b) the name of the case reporter already conveys the name of the court and its jurisdiction.
See The University of Akron's Bluebook Quick Reference: Abbreviations and How-tos for help with abbreviations.
See Publication Manual, 11.4