Helgeson, E. A. (1957). Methods of weed control. Food and Agriculture Organization of the United Nations.
Chicago-referens (17:e uppl.)Helgeson, Earl A. Methods of Weed Control. Rome: Food and Agriculture Organization of the United Nations, 1957.
MLA-referens (9:e uppl.)Helgeson, Earl A. Methods of Weed Control. Food and Agriculture Organization of the United Nations, 1957.
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