[This is not a letter TO the editor. It's for the information of your sub-editors and headline writers].
A county = Xian. 西安
The city = Xi'an. 縣
The apostrophe is important as it shows the word is to be read as two characters (西安) and not one character (縣).
This relates to a recent headline I saw in the Post which mistakenly was "Xian" when it should have been Xi'an.
From your pedantic reader....