What Design Patterns can I see in this diagram?

Hi, I'm new here, and I was wondering if anyone could help me determine what Design Patterns are being used in this class diagram?
I've been given certain class relationships and I made this diagram using them. Now the next step in my work is to decide which Design Patterns are being used in this diagram. If anyone could help me, I'd be very grateful.

The Disk class is generalized from Medijum (Media).

Translations, just in case:
Delo - work (as noun; someone's work)
...naziv - name

Medijum - Media

Osoba - Person
...ime - name
...prezime - last name
...jmbg - personal ID

Kopija - Copy
Kaseta - Cassette

Glumac - Actor
...glumi - acts

Reziser - Film Director
...snimiFilm - film a movie / shoot a movie

Disk - Disc

Radnik - Worker / Employee
...iznajmiIzdanje - rent an edition
...vodiEvidenciju - make evidence of rental

Fotograf - Photographer
...slikaj - take a photo

Izdanje - Edition
MiniDV - MiniDV
VHS - VHS
Film - Film
CD - CD
DVD - DVD
Fotografija - Photography

Videoteka - video (rental) library
...brojIzdanja - number of editions
...dodajPozajmicu - add a rental

I think relations are pretty obvious, but if you need translation, tell me.
The image of the diagram is in the link.

http://freepicupload.com/images/149Capture.png
Thanks!