Question: Arline, your submission guidelines say a possessive that ends in S still gets an apostrophe S, but I was always taught it gets the S without the apostrophe. Can you explain why you are different? Just wondering....
Answer: Sure. Publishers, at least most of the professional ones, use the Chicago Manual of Style and that rulebook says to do it that way. Most of us had Strunk & White (British authors), or other college stylebooks and they say the apostrophe without the S.
Rules vary from stylebook to stylebook. I have to watch out that I don't automatically follow the AP Handbook, as that's what I used on the newspaper....
Here's the whole set of rules for apostrophes:
Apostrophes are used in contractions, that is a shortened version of two words, but never in abbreviations. Can’t instead of can not, it’s for it is (the possessive form of “it” never takes an apostrophe), and didn’t instead of did not. But CDs wouldn’t take an apostrophe.
Apostrophes (usually apostrophe followed by an s) are used, for possessive clauses. Mandy’s house. Tammy’s CDs.
The possessive forms of proper names take an apostrophe s even if they already end in s, such as Silas’s car. But plural nouns and pronouns get the apostrophe without the s in the plural form. I visited Mandy’s parents’ house. The plural form of proper names get an “es” rather than a plain s, and no apostrophe. Both the following are correct. “The Williams’ car,” for plural possessive that says the car belongs to the whole family, and “The Williamses came to dinner,” for plural.
Don't forget that grammar rules are different in England, so the S' without the following S for plural possessives is printed that way in all books published in England and grammar and spelling checkers set for UK English will ask for them that way.