Bagaimana menentukan headword dalam noun phrase ?

"Noun phrases must contain a head. Most frequently this will be a noun or pronoun, but occasionally it can be an adjective or determiner. The heads of noun phrases can be identified by three tests:
1. They cannot be deleted.
2. They can usually be replaced by a pronoun. 3. They can usually be made plural or singular (this may not be possible with proper names).