Friis, R. H. (2012). Essentials of environmental health (2nd ed.). Jones & Bartlett Learning.
Dyfyniad Arddull ChicagoFriis, Robert H. Essentials of Environmental Health. 2nd ed. Sudbury, MA: Jones & Bartlett Learning, 2012.
Dyfyniad MLAFriis, Robert H. Essentials of Environmental Health. 2nd ed. Jones & Bartlett Learning, 2012.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.