Original sentence: These interests led to two of his books, the Remarks Made on a Tour to Prairie du Chien (1831) and his most mature thoughts on the subject expressed in An Essay on Education  (1841)
Edited sentence: These interests led to two of his books, the Remarks Made on a Tour to Prairie du Chien (1831), which includes an interview with the infamous Sauk leader Quashquame, and An Essay on Education  (1841), which contained his most mature thoughts on the subject