possesives in -s

> From:    Roger Mills <romilly@...>
> Subject: Re: interestin' factoids (mostly language-related)
>
> I've been taken to task for making the possessive of names ending in -s
with
> the simple apostrophe-- Mills' theory, Geurtjens' dictionary, Mr. Roberts'
> rank.....
> which I think is OK in British usage.  Or am I wrong on all counts?
I was taught (in school, I suppose) that -s names always take full 's
(Mills's) except for "Jesus".
I don't know whether or not I speak it that way, though.

     *Muke!