Michael Billig argues that when looking at all three studies, Sherif's work involves not just two groups but three, the experimenters are part of the system as well (Billig, 1976).

Michael Billig认为从这三项研究来看，Sherif的工作中涉及到的不只是两个组，而是三个。实验者本身同样也是系统中的一部分(Billig 1976)。

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Both of these manoeuvres would be less hazardous if the pilot could call on a second source of power to turn the blades for a few seconds while he was performing them, and Jean-Michel Billig and his team at Eurocopter (part of EADS, an aerospace and defence group) hope to provide just that.

ECONOMIST: Monitor