1. BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, OIML, The International Vocabulary of Metrology – Basic and general concepts and associated terms (VIM), JCGM 200:2008, http://www.bipm.org/en/publications/guides/vim.html , entry 2.3
2. BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, OIML (2008) The international vocabulary of metrology—basic and general concepts and associated terms (VIM), JCGM 200:2008. http://www.bipm.org/en/publications/guides/vim.html , entry 2.41, note 1
3. BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, OIML (2008) The international vocabulary of metrology—basic and general concepts and associated terms (VIM), JCGM 200:2008. http://www.bipm.org/en/publications/guides/vim.html , entry 5.12
4. BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, OIML (2008) The international vocabulary of metrology—basic and general concepts and associated terms (VIM), JCGM 200:2008. http://www.bipm.org/en/publications/guides/vim.html , entry 2.43
5. BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, OIML (2008) The international vocabulary of metrology—basic and general concepts and associated terms (VIM), JCGM 200:2008. http://www.bipm.org/en/publications/guides/vim.html , entry 2.43, note