The second edition of Quantities, Units and Symbols in Physical Chemistry (ISBN 0-632-03583-8), also known as the Green Book, was edited by I. Mills, et al., is published by the IUPAC, establishing standards for nomenclature in Chemistry.
The green books are direct successors to the "Manual of Symbols and Terminology for Physicochemical Quantities and Units" prepared for publication on behalf of the Physical Chemistry Division of IUPAC by M. L. McGlashen in 1969. A full history of the 'Green Books" is provided in the historical Introduction to the 3rd Edition. Information in the Green book is synthesized from IUPAC, IUPAP and ISO recommendations including in part on the IUPAP red book and the ISO 31 standards. The 2nd edition has been available online as a PDF file, and the third edition will be available as a pdf one year after publication. It is an excellent source for knowledge for how to handle quantities, units and symbols in science.