Most of the European manuals/official regulation documents (maybe except for France) are largely based on USPA SIM. Most of the heavy lifting on writing the lessons learned, reports, manuals and examining incident is done by USPA, BPA (British Skydiving) and APF. They are also associations/clubs that promote the sport of skydiving with a large membership base. In Italy the organization responsible for skydiving regulation/manuals is ENAC (Italian Civil Aviation Authority), which is like FAA in the USA, making it a little out of touch from the skydiving world. They lay out some brief common sense rules for drop zones to follow and some of the discretion/interpretation is left to the drop zone operators. The official documents exist, is that they are a product of bureaucratic entities with questionable competencies in the filed of skydiving who try to fill the regulation void the best they can, if you want to be on the safe side just follow the USPA SIM.