Here’s a grammatical goof of the Yahoo! front page editors’:
Yes, that’s the editors’ grammatical goof. They should have used a double possessive in that sentence: Teammates of Therese Sjogran’s.
It’s called a double possessive because the preposition of forms a possessive and the apostrophe and S also form a possessive. And there’s an actual rule about its use. According to the Associated Press Stylebook:
“Two conditions must apply for a double possessive: 1. The word after of must refer to an animate object, and 2. The word before of must involve only a portion of the animate objects possessions.”
Here’s how I decide if a possessive is required after of: Substitute a pronoun for the term after of. If a possessive pronoun sounds right, use a possessive form of the term. For example, “teammates of hers” sounds right to me; “teammates of her” does not. Of course, this method only works if you have an accurate “ear” for English.
Another way to avoid making a mistake is to avoid the double possessive entirely. In this case, you would write “Therese Sjogran’s teammates” and be sure you’re not making a grammatical gaffe.