source of the CODATA internationally recommended values
The values of the constants provided at this site are recommended for international use by CODATA and are the latest available. Termed the "2018 CODATA recommended values," they are generally recognized worldwide for use in all fields of science and technology. The values became available on 20 May 2019 and replaced the 2014 CODATA set. They are based on all of the data available through 31 December 2018. The 2018 adjustment was carried out under the auspices of the CODATA Task Group on Fundamental Constants.
Searchable bibliography on the constants
This bibliography gives citations for the most important theoretical and experimental publications relevant to the fundamental constants and closely related precision measurements published since the mid 1980s, but also including many older papers of particular interest, some of which date back to the 1800s.