Columbia subject headings:
Bulgaria--Foreign economic relations--United States.
Investments, American--Law and legislation--Bulgaria.
Investments, Foreign--Law and legislation--United States.
United States--Foreign economic relations--Bulgaria.
Harvard subject headings:
Bulgaria--Foreign economic relations--United States.
Investments, American--Law and legislation--Bulgaria.
Investments, Foreign--Law and legislation--United States.
United States--Foreign economic relations--Bulgaria.
Princeton subject headings: