Columbia subject headings:
Technological innovations--Europe, Eastern--Congresses.
Technological innovations--Europe--Congresses.
Working class--Europe, Eastern--Congresses.
Working class--Europe--Congresses.
Harvard subject headings:
Technological innovations--Europe, Eastern--Congresses.
Technological innovations--Europe--Congresses
Working class--Europe, Eastern--Congresses.
Working class--Europe--Congresses.
Princeton subject headings:
Labor--Europe, Eastern--Congresses.
Labor--Europe--Congresses.
Technological innovations--Europe, Eastern--Congresses.
Technological innovations--Europe--Congresses.