1. World Meteorological Organization, Guidelines for the Measurement of Atmospheric Carbon Monoxide (WMO TD No. 1551), 2010. http://www.wmo.int/pages/prog/arep/gaw/gaw-reports.html.
2. Website of accreditation field of National Institute of Technology and Evaluation (NITE). http://www.iajapan.nite.go.jp/jcss/en/index.html.
3. Gas Analysis – Preparation of Calibration Gas Mixtures – Gravimetric Methods;International Organization for Standardization, ISO6142:2001,2001
4. P. Howarth, F. Redgrave, Metrology – in Short, EURAMET, 3rd ed., Braunschweig, 2008. Schultz Grafisk; Copenhagen.
5. Reference Materials – General and Statistical Principles for Certification;International Organization for Standardization, ISO Guide 35:2006,2006