Why does the URL https://www.iupac.org/cms/wp-content/uploads/2015/07/Green-Book-PDF-Version-2011.pdf (ending in 2011) contain the Green Book labelled 2007, and reprinted in 2008? Does a 2011 edition exist and they just uploaded the wrong file?
Same goes for the URL http://media.iupac.org/publications/books/gbook/IUPAC-GB3-2ndPrinting-Online-22apr2011.pdf (containing the exact same file).
And there is the version https://www.iupac.org/fileadmin/user_upload/publications/e-resources/ONLINE-IUPAC-GB3-2ndPrinting-Online-Sep2012.pdf with different water mark, one page more, and the front matter in a different order.