This is an alternative way to do a riffle shuffle by smearing the two halves in a circular configuration and having the spectator push them together. While Lennart Green invented it independently and made it popular, Reinhard Müller found a previous source for the same idea: It is part of Charles Nyquist and Jack McMillen's “The San Francisco Shuffle” in Genii, Vol. 14 No. 3, Nov. 1949, p. 76.