We wish to thank John Lewis for stimulating our interest in the lower-order models. When this was in progress, Dan Dobrovolschi of the National Meteorological Administration in Bucharest, Romania, suggested that interpretation of heteroclinic orbits is an interesting problem, which provided further impetus for this work. We wish to record our sincere thanks to Alex Gluhovsky, Yunheng Wang, and the two anonymous reviewers whose comments greatly improved the presentation.
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