Please answer a question about the following article about 51st state:

This constitution was created when the U.S. Congress directed local government to organize a constitutional convention to write the Puerto Rico Constitution in 1951. The acceptance of that constitution by Puerto Rico's electorate, the U.S. Congress, and the U.S. president occurred in 1952. In addition, the rights, privileges and immunities attendant to United States citizens are "respected in Puerto Rico to the same extent as though Puerto Rico were a state of the union" through the express extension of the Privileges and Immunities Clause of the U.S. Constitution by the U.S. Congress in 1948.

What clause gives Puerto Rican citizens the same rights as US citizens?
Privileges and Immunities Clause