Hello Frederico, happy new year to all,
Beautiful bookcase, very convincing simplicity.
I also found the joinery very interesting but did'nt get anything from the web (exept that pdf in italian), so I made a request at our local Wรผrth store.
Took them a while to find out that this particular product (plastic rail invisible fitting - whatever) can only be ordered if you are a customer based in italy - meaning you need to have a italian cusomer account at Wรผrth. Hm, Could that be for tax reasons?
However, now that we have found you Federico, and you have found this secret market niche, you might make a lot of bucks along the way
cheers
alexander