I haven't update this space for quite a long time.The most important reason is the mid-term exam.Advanced micro,advanced macro and statistical inference,these three are really difficult for me.So I have to spend most of my time in the library during the passed two weeks and put this aside temporarily.Another reason is that I feel a little bit sad because I found my English is really poor (especially when I read Cohen's space) and doubt that whether I can improve my written English in this way. Actually,I have made a decision  that I will try to recit the BOOK THREE of NCE and one of my roommate said he would join me.That's good, for if I just do this alone I know I would give it up very quickly.