the talbot is an SI-unrecognised name for the SI unit lumen second. Frequently, a non-SI metric unit is related to an SI unit through a power-of-ten factor, but not one that has a metric prefix, e.g., = , The angstrom ( = ), still used in various fields, etc. (and correspondences like ≘ ). Finally, there are metric units whose conversion factors to SI units are not powers of ten, e.g., and . Some SI-unrecognised metric units are still frequently used, e.g., the calorie (in nutrition), the rem (in the US), the jansky (in radio astronomy), the gauss (in industry) and the CGS-Gaussian units more generally (in some subfields of physics), the metric horsepower (for engine power, in most of the non-English speaking world), the kilogram-force (for rocket engine thrust, in China and sometimes in Europe), etc. Others are now rarely used, such as the sthène and the rutherford. See also Non-SI units mentioned in the SI Notes References Further reading Unit Systems in Electromagnetism MW Keller et al. (PDF) Metrology Triangle Using a Watt Balance, a Calculable Capacitor, and a Single-Electron Tunneling Device "The Current SI Seen From the Perspective of the Proposed New SI" (PDF). Barry N. Taylor. Journal of Research of the National Institute of Standards and Technology, Vol. 116, No. 6, Pgs. 797–807, Nov–Dec 2011. B. N. Taylor, Ambler Thompson, International System of Units (SI), National Institute of Standards and Technology 2008 edition, . External linksOfficial BIPM – About the BIPM (home page) BIPM – measurement units BIPM brochure (SI reference) ISO 80000-1:2009 Quantities and units – Part 1: General NIST On-line official publications on the SI NIST Special Publication 330, 2019 Edition: The International System of Units (SI) NIST Special Publication 811, 2008 Edition: Guide for the Use of the International System of Units NIST Special Pub 814: Interpretation of the SI for the United States and Federal Government Metric Conversion Policy Rules for SAE Use of SI (Metric) Units EngNet Metric Conversion Chart Online Categorised Metric Conversion CalculatorHistory LaTeX SIunits package manual gives a historical background to the SI.Research''' The metrological triangle Recommendation of ICWM 1 (CI-2005) Spelling and usage USMA Frequently Asked Questions about SI Systems of units International standards