1. People lead to people
2. People lead to documents
3. Documents lead to documents
4. Documents lead to people
Secondhand Information
Must be used for checked for bias or error
Seeking political feasibility data
Multiple Source of Firsthand Information
Suppose you wish to know about the past relationship between the police and fire departments. If for some reason you do not wish to ask the fire chief, it is always possible to ask the police chief, since she has been a partner to these relations as much as the fire chief.