Chow, J. C., Watson, J. G., Hackett, E. I., Hinsvark, B. A. (2008). Method No. 303A: General method for the preparation and extraction of environmental samples for trace metal or ion analysisMethod No. 303A: General method for the preparation and extraction of environmental samples for trace metal or ion analysis, In Methods of Air Sampling and Analysis, 4th ed., Air and Waste Management Association: Pittsburgh, PA