There is a lot of confusion about the possessive form of singular proper nouns that end in "s". I've seen it both ways and have never found a consistent pattern in American English. Historical figures usually just get an apostrophe, and normal people get an apostrophe and an "s". Example: "Jesus' desciples" vs "Chris's bicycle". There are exceptions to even this rule, however, such as "Zeus's infidelity". For regular nouns, it seems more consistent ("for goodness' sake" but never "for goodness's sake"). Does anyone know a concrete rule for this?