reviewed by Ralf Laue
Rating: ★★★★★ (Date Added: Thursday 27 August, 2020)
It's really great principle that has been used in many other tricks later (including a Tenyo trick in 1997). Before buying, have a look into your library. It is not unlikely that you already have a description as it has been also published in Bob Hummers Seleted Secrets, Fulves' Self-working Number Magic and Gardner's Mathematics, Magics and Mystery.