Columbia subject headings:
Petroleum workers--Labor unions--Mexico.
Petróleos Mexicanos.
S.T.P.R.M. (Organization)
Harvard subject headings:
Petroleum workers--Labor unions--Mexico.
Petróleos Mexicanos
S.T.P.R.M. (Organization)
Princeton subject headings:
Mexico--Politics and government--1970-.
Petroleum industry and trade--Mexico.
Petroleum workers--Labor unions--Mexico.
Petróleos Mexicanos.
S.T.P.R.M. (Organization)