Columbia subject headings:
Ammonia industry--Technological innovations.
Ammonia industry--United States.
Manufacturing processes--Case studies.
Technological innovations--United States--Case studies.
Harvard subject headings:
Ammonia industry--Technological innovations.
Ammonia industry--United States.
Manufacturing processes--Case studies.
Technological innovations--United States--Case studies
Princeton subject headings:
Ammonia industry--Technological innovations.
Ammonia industry--United States.
Case studies.
Manufacturing processes--Case studies.
Technological innovations--United States--Case studies.