How important are are the use of sources in studying a history

Who was one of the greatest playwrights in the world , composing such classics ans macbeth, romeo and juliet, and henry v a. william shakespeare b. francis drake c. sir walter raleigh d. edmund spenser

The rise of advertising in the 1920s. i am good with seeing how advertisements shape the roaring twenties and how it developed a new way of life through modern days. but i am not sure what the details of advertising in the 1920s were. if possible can you send me links (preferrably credential links) to sources that maybe show like the first company to start advertising through the radio, how advertising benefits (statistics graphs), etc.

Oraccording to document 3,do you think napoleon is a democratic reformer imperial dictator? explain.