Temple PJ, Sun JE-J, Krause GHM.
Peroxyacetyl nitrates (PAN) and other minor pollutants. Recognition of Air Pollutant Injury to Vegetation: A Pictorial Atlas. 2nd Edition. Air & Waste Management Association, Pittsburgh, PA. 1998 :pp 6-1 to 6-2.
Kothny EL.
Palladium in plant ash. Plant and Soil. 1979 ;(53):547-550.