MLA

Kissinger, Henry, 1923-2023. "Preliminary Report on American Opinion about Vietnam" by Lloyd A. Free. Box 231, folder 8. 1968 March. https://collections.library.yale.edu/catalog/11786253.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 231, folder 8"])(1968 March)["Preliminary Report on American Opinion about Vietnam" by Lloyd A. Free]. https://collections.library.yale.edu/catalog/11786253.