MLA

Boswell, James, 1740-1795. The life of Samuel Johnson, LL.D. : comprehending an account of his studies and numerous works in chronological order ... : the whole exhibiting a view of literature and literary men in Great-Britain for near half a century during which he flourished. MDCCXCI [1791]. https://collections.library.yale.edu/catalog/31920963.

APA, 6th edition

Boswell, James, 1740-1795. (MDCCXCI [1791])[The life of Samuel Johnson, LL.D. : comprehending an account of his studies and numerous works in chronological order ... : the whole exhibiting a view of literature and literary men in Great-Britain for near half a century during which he flourished]. https://collections.library.yale.edu/catalog/31920963.