An essay on indigestion :

MLA

Johnson, James. An Essay On Indigestion . 9th ed. improved London,: S. Highley, 1836.

APA

Johnson, J. (1836). An essay on indigestion . 9th ed. improved London,: S. Highley.

Chicago

Johnson, James, An Essay On Indigestion :. 9th ed. improved London,: S. Highley, 1836.