Original sentence: In October 1945 Boris Polevoy was finally able to enter graduate school at the History Department of Leningrad University, working on a a dissertation on the history of the US foreign policy in the mid-19 century, and teaching classes at his department
Edited sentence: In October 1945 Boris Polevoy was finally able to enter graduate school at the History Department of Leningrad University, working on a dissertation on the history of the US foreign policy in the mid-19 century, and teaching classes at his department