Não informado. (1951). FAO Fertilizer Yearbook. Food and Agriculture Organization of the United Nations.
Chicago-referens (17:e uppl.)Não informado. FAO Fertilizer Yearbook. Rome: Food and Agriculture Organization of the United Nations, 1951.
MLA-referens (8:e uppl.)Não informado. FAO Fertilizer Yearbook. Food and Agriculture Organization of the United Nations, 1951.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.