where is the ring of blades&+15 thievery amulet?

Hi,

I searched all over the internet but couldn't find an answer:

whereexactly can you find the "ring of blades" (+20 thievery)? also, what amulet gives you +15 thievery, and where can you find it? (i have "thief's amulet" but it only gives +10 thievery).

thanks!