Resolution 3 of the 10th CGPM (1954)
Definition of the thermodynamic temperature scale
The 10th Conférence Générale des Poids et Mesures decides to define the thermodynamic temperature scale by choosing the triple point of water as the fundamental fixed point, and assigning to it the temperature
NOTE
The 13th CGPM in 1967 explicitly defined the kelvin (Resolution 4).