Columbia subject headings:
Phosphorus--Environmental aspects--Great Lakes (North America)--Congresses.
Sewage disposal in rivers, lakes, etc.--Great Lakes (North America)--Congresses.
Water quality management--Great Lakes (North America)--Congresses.
Harvard subject headings:
Phosphorus--Environmental aspects--Great Lakes--Congresses.
Sewage disposal in rivers, lakes, etc.--Great Lakes--Congresses.
Water quality management--Great Lakes--Congresses.
Princeton subject headings: