这个扩展被称为格罗坦狄克群。

This extension is known as the Grothendieck group.

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克雷布斯假设，小群的苍鹭是在观察，它们可能会跟随被观察的苍鹭去更好的觅食池，那里通常会吸引更多的鸟类。

Krebs hypothesizes that the herons in smaller flocks are watching for herons that they might follow to better feeding pools, which usually attract larger numbers of the birds.

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其中最早的，如公元前4500年的埃利都以及之后1000年出现的乌鲁克，都以用泥砖建造的令人惊叹的庙宇群为中心。

The earliest, that of Eridu, about 4500 B.C.E., and Uruk, a thousand years later, center on impressive temple complexes built of mud brick.

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