[原创]PhD申请材料里的 statement of purpose 该怎么写啊？有参考么？求助ing~~~

这是密歇根大学商科PhD application checklist 上写的：

Statement of Purpose
This is one of the most important documents in your application and should clearly convey the following:
• A clear idea of why you wish to pursue a Ph.D. in business administration
• What questions or problems interest you
• How you will address these problems
• Why you wish to pursue your doctoral degree at the University of Michigan

请问有哪位仁兄写过或者给我推荐一下比较好的范例呢？不胜感激阿~~~~