MLA

Wallerstein, Immanuel Maurice, 1930-. Portuguese-British Alliance. Box 3. undated. https://collections.library.yale.edu/catalog/17317506.

APA, 6th edition

Wallerstein, Immanuel Maurice, 1930-. (["Box 3"])(undated)[Portuguese-British Alliance]. https://collections.library.yale.edu/catalog/17317506.