Possible Duplicate:
What is the correct possessive for nouns ending in s?
When did it become correct to add an 's' to a singular possessive already ending in 's'?
I've always heard that when talking about stuff belonging to either a Jones or many Jones, you'd write Jones' (pronounced "Joneses"). But recently I've stumbled upon a book which consistently uses Jones's when talking of a single Jones.
What's the correct way of using possesives?