Acquisition of additional sites

In addition to the properties described in section 410z of this title, the Secretary shall study the properties described in this section to determine the feasibility and suitability of including them within the Boston National Historical Park. In making such studies, he may enter into tentative agreements with any owners thereof for their inclusion in said park and he may enter into options, for a nominal consideration, for the purchase of such properties, but no additional properties may be added to the park except by an act of the Congress. Studies shall be made of the following properties: The Secretary may identify other significant sites of the colonial and Revolutionary periods of American history in the city of Boston, Massachusetts, and its environs, which are related to the historical park created by this subchapter, and, with the consent of the owner or owners thereof, may mark them appropriately and make reference to them in any interpretive literature.