Columbia subject headings:
Airlines--Employees--United States.
Collective labor agreements--Aeronautics--United States.
Collective labor agreements--Railroads--United States.
Railroads--United States--Employees.
Harvard subject headings:
Airlines--United States--Employees.
Collective labor agreements--Aeronautics--United States.
Collective labor agreements--Railroads--United States.
Railroads--United States--Employees
Princeton subject headings:
Airlines--Employees--United States.
Collective labor agreements--Aeronautics--United States.
Collective labor agreements--Railroads--United States.
Railroads--United States--Employees.