I just voted and noticed that
Lois's is far behind. We're in the minority here, Tricia!
Actually, in my two first stories you'll notice that I've used
Lois' When Tricia started to BR for me she told me to use
Lois's and of course I did. Anything to keep my BR happy!
That's the way I was taught in school, anyway. Initially, I started writing
Lois' because I'd seen it in so many fanfics; I just assumed it had to be the American way.
Ursie