Columbia subject headings:
Civilization, Medieval--12th century.
Crusades--Third, 1189-1192.
Frederick I, Holy Roman Emperor, approximately 1123-1190.
Military history, Medieval.
Harvard subject headings:
Frederick I, Holy Roman Emperor, approximately 1123-1190.
Princeton subject headings:
Crusades--Third, 1189-1192.
Frederick I, Holy Roman Emperor, approximately 1123-1190.
Military history, Medieval.