One way to find reference material pertaining to mission work and philosophy is to browse the Reference Collection. A good place to start is:
You have access to a wide variety of titles because of the sharing agreement Northwestern has with seven other college and university libraries in the Twin Cities area. Be sure to begin your research early so that you can take advantage of this wide variety of resources. Search in Library Search for applicable books using keywords associated with your research interest.
Example searches include:
You can use ProQuest Religion to find scholarly, full-text articles on the topics of theology, religious studies, philosophy, ethics, doctrines, and religious history.