The correct answer to this open question is the following.
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The two seminal documents that King reference as historical allusions on this page are the Constitution of the United States and the decision of the Supreme Court in 1954 that outlawed racial segregation in public schools.
The effect that these seminal documents have on King's audience is to move the audience into action and not passively read and stay there, doing nothing against the racial injustices against African Americans and other minorities.
We are talking about the important document called "Letter from a Birmingham Jail," written by social activist and civil rights leader Dr. Martin Luther King Jr, when he was in Birmingham prison, in Alabama.
There, he referred to two types of laws: unjust and just legislation.