Of-Genitiv i Engelsk?!

Hej alle:)

Jeg har fået til opgave i engelsk at finde alle genitivformer i en tekst, og gøre rede for hvorfor der er brugt of-genitiv og apostrofgenitiv;)

Jeg kan godt finde apostofgenitiverne, kan bare ikke forklare hvorfor de er blevet brugt... Udover dette kan jeg slet ikke gennemskue of-genitiv...
Håber at I gider hjælpe - jeg mangler ikke løsningen på opgaven - blot en forklaring:)

Last week's papers had been full of stories about violence among teenagers, especially among
boys. The front page story was about the death of a thirteen-year-old boy, who had been
walking in one of the dangerous areas of the city, and had been stabbed from behind by a
member of a teenage gang. The next day the members of the gang maintained that they didn't
remember much of last night's events, but they did remember that the owner of the pub where
they had spent the evening had thrown them out. Afterwards they had gone to a friend of one
of the gang members to have a few more drinks, and then they had continued their drinking at
somebody else's place ? they remembered neither the name of the person nor of the street
where he lived, but they thought it was in the neighbourhood of St. Paul's. The fingerprints of
one of the gang members were found on the knife that had been left in the young boy's back,
and the killer was sentenced to seven years' imprisonment
 

På forhånd tak! :)