Columbia subject headings:
Industries--Russia (Federation)--Mari El.
Labor productivity--Russia (Federation)--Mari El.
Working class--Russia (Federation)--Mari El.
Harvard subject headings:
Industries--Russia--Mari El.
Labor productivity--Russia (Federation)--Mariĭskai︠a︡ A.S.S.R.
Working class--Russia (Federation)--Mariĭskai︠a︡ A.S.S.R.
Princeton subject headings:
Industries--Russia (Federation)--Mari El.
Labor productivity--Russia (Federation)--Mari El.
Working class--Russia (Federation)--Mari El.