Columbia subject headings:
Africa, Sub-Saharan--Commerce--History--Congresses.
Transport workers--Africa, Sub-Saharan--History--Congresses.
Harvard subject headings:
Africa, Sub-Saharan--Commerce--History--Congresses.
Transport workers--Africa, Sub-Saharan--History--Congresses.
Princeton subject headings:
Africa, Sub-Saharan--Commerce--History--Congresses.
Transport workers--Africa, Sub-Saharan--History--Congresses.