You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "who has the power to establish post offices?" whose answer is Congress.
Each document should contain about 30 words, and these documents should contain useful information.

Query: who has the power to establish post offices in the United States
Useful Output:

Doc 1: The expressed power to establish a post office is granted to Congress by the Constitution, specifically in Article I, Section 8, Clause 7. This
Doc 2: The Constitution grants Congress “the Power to establish Post Offices and Post Roads.” The Supreme Court has interpreted the post office
Doc 3: In June 1788, the ninth state ratified the Constitution, which gave Congress the power “To establish Post Offices and post Roads” in Article I,
Doc 4:  of the U.S. Constitution empowered Congress to establish post offices and post roads. Congress exercised those powers with the passage of The Post Office
Doc 5: Answer: Article 1, Section 8 clause 7 of the U.S. Constitution grants Congress the power to establish post offices and post roads. Section 8 is