Columbia subject headings:
Luhmann, Niklas, 1927-1998.
Social systems.
Sociology.
Harvard subject headings:
Luhmann, Niklas, 1927-1998
Social systems.
Sociologists--Germany--Biography.
Sociology--Germany.
System theory
Princeton subject headings:
Luhmann, Niklas, 1927-1998.
Social systems.
Sociology.