MLA

Elizabeth I, Queen of England, 1533-1603. Letter from Queen Elizabeth I to Lady Elizabeth Southwell, 1598 October 15 : manuscript. 1598 October 15.. https://collections.library.yale.edu/catalog/16807670.

APA, 6th edition

Elizabeth I, Queen of England, 1533-1603. (1598 October 15.)[Letter from Queen Elizabeth I to Lady Elizabeth Southwell, 1598 October 15 : manuscript]. https://collections.library.yale.edu/catalog/16807670.