We don't say anything about implicitly here, we're talking about a closed system, so there's no mass leaving the system.

我们不讨论,这是隐含条件，因为我们讨论的是孤立系统，因此系统没有物质流失。

麻省理工公开课 - 热力学与动力学课程节选

Because we don't really consider Western Literature to have an actual closed canon of authoritative texts.

因为我们并不认为西方文学,具有权威文本的固定标准。

耶鲁公开课 - 新约课程节选