Columbia subject headings:
Agriculture--Early works to 1800.
Agriculture--England--Early works to 1800.
Harvard subject headings:
Agricultural machinery--Early works to 1800.
Agriculture
Agriculture--Early works to 1800
Agriculture--England
Agriculture--England--Early works to 1800.
Cropping systems--Early works to 1800.
Crops--Early works to 1800.
Princeton subject headings: