Which is the best source of historical evidence to learn about how an event unfolded?

First person evidence; i.e. Evidence from someone who was there when it happened. Original paintings, letters and pictures. Biographies about their lives.

- "bill clinton ( the 42nd u.s. president, served in office from by low unemployment, declining crime rates and a budget surplus. during clinton's second term, the u.s. economy was healthy, unemployment was low and the nation experienced a major technology boom and the rise of the internet."