Which two seminal us documents does king refer to on the last page? why does he include these historical references what impact do they have on his argument

The two documents mentioned by Dr. Martin Luther King would be the U.S. Constitution and the 1954 Supreme Court Decision that outlawed segregation in public schools.

Explanation:

In Letter from a Birmingham Jail, MLK countered his critics who were calling his actions extreme and he drew attention to the need for action at a time when many Americans were passively condoning racism by remaining silent on the issue and failing to support those who were working for change.  MLK appeals to documents at the end of his letter that are legitimately part of the US system like the Constitution and the 1954 Supreme Court decision against segregation to make the point that the segregation situation is unjust and against the law.