MLA

Kissinger, Henry, 1923-2023. "Acht Uhr Abmarsch bei Helmstedt," interview with Hans Schmelz and Conrad Ahlers, Der Spiegel. Box 751, folder 12. Undated, circa 1977-circa 2006. https://collections.library.yale.edu/catalog/11782221.

APA, 6th edition

Kissinger, Henry, 1923-2023. (["Box 751, folder 12"])(Undated, circa 1977-circa 2006)["Acht Uhr Abmarsch bei Helmstedt," interview with Hans Schmelz and Conrad Ahlers, Der Spiegel]. https://collections.library.yale.edu/catalog/11782221.