Taylor, Barry N. (ed.). «The International System of Units (SI)». Special Publication 330. Gaithersburg, Maryland: National Institute of Standards and Technology (NIST), 2001. Arxivat de l'original el 2018-12-25. [Consulta: 17 setembre 2012].
Taylor, Barry N. (ed.). «The International System of Units (SI)». Special Publication 330. Gaithersburg, Maryland: National Institute of Standards and Technology (NIST), 2001. Arxivat de l'original el 2018-12-25. [Consulta: 17 setembre 2012].