英语听力中"in seach of"和"in a seach for"怎么区分呢？我听不出区别

语法学家Shaw早在1970年就曾指出：“in search for is also common，but in search of is preferred.”(“in search for也是通用的，但是in search of则更好”)。举例：
1．…while in search for a title for his first book of poems．……在他寻找他的第一部诗集的书名时。
2．…not the businessman in search for orders or for the secrets of know-how．……不是寻找订单或技术秘密的商人。
刚看到一个新闻标题：Pfizer Assists World Health Organization In Search For New Treatments Against Diseases Of The Developing World