I know there's a lot of good work online about it, including from pecunium, but I don't have specific locations handy to memory.
Also, anything solid about the long term effects of torture which doesn't leave visible marks would be appreciated.
Addendum:Eric says (in comments) that he's against torture. However, he seems to define anything which doesn't leave marks as not being torture.
I'll be working on sorting this stuff out when I comment over there.