The NIST Reference on Constants, Units and Uncertainty Information at the foundation of modern science and technology from the Physical Measurement Laboratory of NIST

CODATA Internationally recommended 2018 values of the
Fundamental Physical Constants

Constants
Topics:
Values
Energy
Equivalents
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Bibliography
Background

Constants
Bibliography

Constants,
Units &
Uncertainty
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  (e.g., electron mass, most misspellings okay)
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NIST Standard Reference Database 121. Last Update to Data Content: May 2019.
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Online: October 1994   -   Last update: May 2019