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Neale's "Sheep and Goats" problem fold is back and down. The next three folds are valley folds, first to the right, then up, then left. After the last fold slide the tab under the double-leaved black triangle at the top left of the square. Glue the tab to the bottom leaf of the triangle. You should now have a square with four black and four white triangles on each side. These are the sheep and goats.

The problem is: By folding only along precreased lines, change the paper to a square of the same size that is all white on one side and all black on the other. In other words, separate the sheep from the goats. It is not easy, but it is a delight to make the moves rapidly once you master the stepsâ€”which I shall diagram in the Answer Section, along with the answer to the tetraflexagon puzzle. (To make the manipulations smoother, it is a good plan to trim a tiny sliver from all single edges after the square has been folded and glued.)

Anyone interested in learning some of Neale's more traditional origami figures will find six of his best (including his Thurber dog) in Samuel Randlett's The Best of Origami (E. P. Dutton, 1963). Some of his dollar-bill folds (including the jumping frog) are in Folding Money: Volume II, edited by Rand-lett (Magic, Inc., 1968).

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