> That's a new one! So, you're saying the plural of GP shouldn't be GPs,> because GPS is another viable acronym?
"GPS TO STOP WORKING BY 2020!"
It's not a case of should or shouldn't, just the option is there to use
an apostrophe to denote plural for the purpose of making the text
clearer to read. It's not normally needed for acronyms (more usually for
letters or numbers), but it's incorrect to state that an apostrophe is
never used for plurarls.
