The third part is some theories about metonymy. This part mainly include the nature of metonymy, content of metonymy and cognitive functions of metonymy.
The fourth part discusses the metonymy motivation of different kinds of euphemism with help of examples from British National Corpus and other literature works. 论英语委婉语的转喻动机(3):http://www.751com.cn/yingyu/lunwen_38258.html