Now, the reason to be interested in them, again, is not because they're frequent.

对这些障碍非常关注的原因,并不是它们很常见

耶鲁公开课 - 心理学导论课程节选

A normal reason for fighting is a dispute about a piece of land that is more or less on the boundary between them, and so that's one aspect of their world.

战争的常见原因就是领土争端,争夺一片或多或少在他们边界之间的领土,这是他们生活的一个部分

耶鲁公开课 - 古希腊历史简介课程节选