Resolution 4 of the 13th CGPM (1967)
Definition of the SI unit of thermodynamic temperature (kelvin)
The 13th Conférence Générale des Poids et Mesures (CGPM),
considering that it is useful to formulate more explicitly the definition of the unit of thermodynamic temperature contained in
decides to express this definition as follows:
"The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water."
See Recommendation 5 (CI-1989) of the CIPM on the International Temperature Scale of 1990.
This definition of the kelvin was abrogated in 2018 by the 26th CGPM (Resolution 1), which became effective in 2019.