Columbia subject headings:
Harvard subject headings:
Airlines--Employees--Labor unions--Portugal--History--21st century--Case studies.
Automobile industry workers--Labor unions--Portugal--History--21st century--Case studies.
Labor unions--Portugal--History--21st century--Case studies.
Telecommunication--Employees--Labor unions--Portugal--History--21st century--Case studies.
Princeton subject headings:
Airlines--Employees--Labor unions--Portugal--History--21st century--Case studies.
Automobile industry workers--Labor unions--Portugal--History--21st century--Case studies.
Labor unions--Portugal--History--21st century--Case studies.
Telecommunication--Employees--Labor unions--Portugal--History--21st century--Case studies.