## Wikipedia - Costante di Planck Planck constant, $$h$$

https://doi.org/10.1351/goldbook.P04685
The Planck constant, $$h$$, is one of seven fixed constants defining the International System of Units, the SI, with $$h = 6.626\ 070\ 15\ \times 10^{-34}\ \text{J}\ \text{s}$$. The Planck constant is considered as a fundamental constant of nature.
Sources:
BIPM, The International System of Units, SI Brochure, 9th ed. (2019) [Terms] [Book]
Newell et al., Metrologia 55, L13-L16 (2018) [Terms] [Book]