The Northern University Working Paper Series is meant to serve as a practical learning tool for Masters level students. The recommended textbook(s) at times have shortcomings vis-à-vis what the tutor would ideally like the students to cover in a particular course. We hope that this gap can be plugged through explanatory materials presented in this series in easy to understand language. In other words, the Working Paper Series will give a reality check in the context of Bangladesh. Therefore, the Working Paper Series is a supplementary tool that can be drawn upon by the tutor as needed.