Columbia subject headings:
Harvard subject headings:
Forced labor--History--Congresses.
Indentured servants--History--Congresses.
Labor contract--History--Congresses.
Labor policy--History--Congresses.
Peonage--History--Congresses.
Slave labor--History--Congresses.
Princeton subject headings:
Forced labor--History--Congresses.
Indentured servants--History--Congresses.
Labor contract--History--Congresses.
Labor policy--History--Congresses.
Peonage--History--Congresses.
Slave labor--History--Congresses.