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Playing card constructions by George W. Hart. He explains how the spheres are made, here.

Notes by Hart:

This page has ideas for two constructions that can be made with playing cards. In each case, the cards are just cut and interlocked without glue or tape.  The larger one, shown at right above, uses 60 cards.  The smaller one, at left, uses only 30 cards, but I think it may be harder to assemble. Together, the two can be made with two decks of cards.  The templates needed to cut the slits for these constructions are given below.

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