1. Eaton , A. 2013 UCMR3---Implications of Measuring at Ultra Trace Levels Proc. AWWA 2013 Ann. Conf. Denver.
2. Informing Regulatory Decisions Using National Occurrence Data;Roberson;Journal AWWA,2012
3. Satterfield , Z. 2004 What Does ppm or ppb Mean? On Tap www.nesc.wvu.edu/ndwc/articles/ot/fa04/q&a.pdf
4. USEPA (US Environmental Protection Agency) 2013 Appendix A to Subpart O---Regulated Contaminants www.epa.gov/ogwdw/ccr/pdfs/regulations_ccr_ccrtable.pdf