History Coursework on african american civil rights

My coursework question is 'to what extent was Lyndon Johnson the most influencial president in improving african american civil rights from 1913-2008' and all ive done so far is some background reading, and an overview of each presidents failures/successes in civil rights. Im going to mainly focus on LBJ, but have been told I need to mention all the presidents from the time period.
I need help finding an analytical quote about each president, the 3 primary sources i need, and also an overview of the format i should use! Thankyou