第四讲 meaning in Chinese

duality and the resulting complications

Lecture series of mobile data services part 4 : short message service
移动数据业务讲座第四讲短消息业务
Lecture on surge protection technology . surge current diverting capacity of surge protection devices
电涌保护技术讲座第四讲电涌保护器的通流容量
Choice and practice of analytical methods in metal analysis lecture 4 determination of titanium in metals and alloys continuation
金属材料分析方法的选择和施行第四讲金属材料中钛的测定续