Before revision: In previous centuries, some independent scholars achieved renown, such as Samuel Johnson and Edward Gibbon during the 18th century and Charles Darwin and Karl Marx in the 19th century, and Sigmund Freud, Sir Steven Runciman and Robert Davidsohn in the 20th century.
After revision: In previous centuries, some independent scholars achieved renown, such as Samuel Johnson and Edward Gibbon during the 18th century and Charles Darwin and Karl Marx in the 19th century, and Sigmund Freud, Sir Steven Runciman , Robert Davidsohn and Nancy Sandars in the 20th century.