UN Style Guide A-Z
W X Y Z
The UN official guide is now
available (changes from 1984 are marked with *):
gastro-enteritis (NSOED, POD, OM), gastroenteritis (ODSWE). I'd go for the first to separate the vowels. Not WHO, though, for whom/which it's gastroenteritis and gastrointestinal (WHO 87).
GATT It's history, but you may still need to refer to it. The UN says it should not be used in references to the Agreement itself (UN:419), a weird choice in view of what the acronym means: General Agreement on Tariffs and Trade. The UN does allow it to denote the Contracting Parties to GATT (no the ) (UN:419).
grey/gray Though MSWord's U.K. English spellchecker says "gray", the Oxford Dictionary for Writers and Editors says use "grey not gray". Note that for HTML editors, "grey" is not a color that Microsoft Browsers understand, only "gray". But others need "grey". So you have to code twice.
ground water (noun) (UN:356) but ground-water (adj.) (UN:356)
guideline/s: these are not in NSOED as entries but both appear in examples and the UN says 'guidelines' can be used (347). POD has' guideline' but ODWE and ODSWE do not.