Columbia subject headings:
Harvard subject headings:
Ecology--Russia (Federation)--Orenburgskai︠a︡ oblastʹ--Congresses.
Orenburgskai︠a︡ oblastʹ (Russia)--Economic conditions--Congresses.
Orenburgskai︠a︡ oblastʹ (Russia)--Geography--Congresses.
Orenburgskai︠a︡ oblastʹ (Russia)--History--Congresses.
Princeton subject headings:
Ecology--Russia (Federation)--Orenburgskai︠a︡ oblastʹ--Congresses.
Orenburgskai︠a︡ oblastʹ (Russia)--Economic conditions--Congresses.
Orenburgskai︠a︡ oblastʹ (Russia)--Geography--Congresses.
Orenburgskai︠a︡ oblastʹ (Russia)--History--Congresses.