On Group Stability in Hierarchies and Networks
解释层级组织为何普遍存在：通过将自主权和否决权分配给特定子群体，层级结构能避免协调中的不稳定，而网络结构则难以做到。
A hierarchical structure is a widespread organizational form in many areas. My aim in this paper is to provide a rationale for this fact based on two premises. First, a group organizes itself so as to achieve efficient coordination. Second, efficient coordination is achieved only if subgroups as well as individuals agree to cooperate. Even in situations in which there are gains to coordination, the agreement of each possible subgroup may be impossible to reach, resulting in instabilities. I argue that a hierarchical organization avoids such instabilities by distributing in an optimal way autonomy and blocking power to a restricted set of subgroups. Comparisons with nondirected networks are drawn.