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It turns out that there are very few groups that are classified as interacting quartets. Most of the ones that are outstanding are shown on pages 4.1 and 4.2. It is surprising that a high percentage of them have a linear arrangement. As in Category 3, the phenomenon is probably related to the chaining in Category 17 and diametric companions in Category 8. In AM 0218-321 one faint arm of the spiral encircles the companion immediately to the north. This object is also illustrated under Category 17.