This technique is also referred to as the count-back force, in which between ten and twenty cards are counted off, then the digits of the number added together and the result counted from the packet to arrive at the force card. In Genii, Vol. 62 No. 4, Apr. 1999, p. 46, Phil Goldstein writes: “The Count-Back Force…seems to have first seen print in Billy O'Connor's 'After the Four Ace Trick' in the June-Sept. 1935 Magic Wand, although there is evidence to suggest that it is older than that.”