1. <publication> Informal name for one of the four standard references on the page-layout and graphics-control language PostScript. The other three official guides are known as the Green Book, the Red Book, and the White Book.
3. <publication> Any of the 1988 standards issued by the ITU-T's ninth plenary assembly. These include, among other things, the X.400 electronic mail specification and the Group 1 through 4 fax standards.