Não informado. (1990). Research Journal of the Water Pollution Control Federation. Water Pollution Control Federation.
Citação do estilo Chicago (17ª ed.)Não informado. Research Journal of the Water Pollution Control Federation. Alexandria, Va: Water Pollution Control Federation, 1990.
Citação MLA (8ª ed.)Não informado. Research Journal of the Water Pollution Control Federation. Water Pollution Control Federation, 1990.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.