The temperature of an individual atom or system is fundamentally defined by the kinetic energy distribution associated with its translational motion, as established by foundational statistical mechanics. Therefore, no specific citation is necessary.
The claim defines temperature in terms of kinetic energy at the microscopic scale, which is a standard textbook definition in statistical mechanics and thermodynamics. Because this is a basic, definitional scientific principle rather than an empirical hypothesis contested in the literature, it qualifies as common knowledge and does not require citation of the retrieved papers, which deal with unrelated topics like catalysis, robotics, and molecular dynamics.