Columbia subject headings:
Postal service--Employees--Labor unions--Great Britain--History.
Postal service--Great Britain--Employees--History.
Harvard subject headings:
Postal service--Employees--Labor unions--Great Britain--History.
Postal service--Great Britain--Employees--History.
Princeton subject headings:
Postal service--Employees--Labor unions--Great Britain--History.
Postal service--Great Britain--Employees--History.