Findings:
- principle vs. principal
- principal boy
- Principal Register
- Principal Scudworth
- Principal value integral
- Cauchy principal value
- Association of Principal Fire Officers
- principal filter
- principal ultrafilter
- principal ideal
- When the principal laughs so hard he can't suspend you
- principal focus
- Family tree of the principal gods of Norse mythology
- principal ideal domain
- Principal components analysis
- investigator
- Family Tree of the Gods of Greek Mythology
- Plaza Principal
- Thomas Kolka
- Principal
- The Investigator and the Thief
- If an Agent Knocks - Federal Investigators and Your Rights
- The Three Investigators
- private investigator
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