Phase four means that a virus has gained the ability to cause community-level outbreaks.

VOA: special.2009.05.06

The classical hoplite formation then was not the long lived military institution of scholarly tradition, but merely one phase in a history of almost four centuries of slow change towards ever denser and more cohesive heavy infantry formations."

这种方阵的形成,并不是经过长期传承的传统军事制度,只是步兵阵型演变的一个阶段,战阵逐渐向更加紧密坚固的步兵阵型转化,而这个变化持续了约有四个世纪"

耶鲁公开课 - 古希腊历史简介课程节选

The classical hoplite formation then was not the long lived military institution of scholarly tradition, but merely one phase in a history of almost four centuries of slow change towards ever denser and more cohesive heavy infantry formations."

这种方阵的形成,并不是经过长期传承的传统军事制度,只是步兵阵型演变的一个阶段,战阵逐渐向更加紧密坚固的步兵阵型转化,而这个变化持续了约有四个世纪"

耶鲁公开课 - 古希腊历史简介课程节选