"The sky of my land is laughing..."
MLA
Lowenfels, Walter, 1897-1976. "The sky of my land is laughing...". Box 157, folder 2690. undated. https://collections.library.yale.edu/catalog/10051175.
APA, 6th edition
Lowenfels, Walter, 1897-1976. (["Box 157, folder 2690"])(undated)["The sky of my land is laughing..."]. https://collections.library.yale.edu/catalog/10051175.