Tolong jelaskan mengenai Sumber Primer dari Andrew Johnson

Ralph W. Haskins, LeRoy P. Graf, and Paul H. Bergeron et al., eds. The Papers of Andrew Johnson 16 volumes; University of Tennessee Press, (1967–2000). ISBN 1-57233-091-0. Includes all letters and speeches by Johnson, and many letters written to him. Complete to 1875.