The Dominic System: A powerful and efficient method for remembering very long numbers.

If you're now skilled in the number rhyme and major system, it's time to upgrade to this system to further increase your powers. This system memorises numbers in sets of 4 which is why it's more efficient. Although a there is another system called the PAO system which encodes 6 numbers at a time, this system is used by 8 times world memory champion so I don't think it's necessary to learn the PAO system which also takes longer.