MLA
Luther, Martin, 1483-1546. In Epistolam Pauli ad Galatas, F. Martini Lutheri Augustiniani, commentarius .... 1519. Richard C. Kessler Reformation Collection. Pitts Theology Library. https://digital.library.emory.edu/purl/709w0vt6c0-cor.
APA, 6th edition
Luther, Martin, 1483-1546. (1519)[In Epistolam Pauli ad Galatas, F. Martini Lutheri Augustiniani, commentarius ...]. Richard C. Kessler Reformation Collection, Pitts Theology Library. https://digital.library.emory.edu/purl/709w0vt6c0-cor.
Chicago
Luther, Martin, 1483-1546, In Epistolam Pauli ad Galatas, F. Martini Lutheri Augustiniani, commentarius ..., 1519, Richard C. Kessler Reformation Collection, Pitts Theology Library. https://digital.library.emory.edu/purl/709w0vt6c0-cor.