Apostrophe after a name ending in 's'

To follow-up the student question earlier today, I double-checked the rule. Apparently it's a matter of style, where some writers use only an apostrophe, and others add the s after the apostrophe too. 

However, the further I looked in it, in terms of the number of sites, it does seem to be slightly in favour of the 's. So it's up to you, follow the crowd, or follow your style (whichever your style is). What is important to keep in mind is to be consistent in your writing.

Finally, one last complication from the University of Bristol.