Klient / server strukturer

this should sort you out fine, if this is not the sort of things you are lookin for then i will need to know a little more about what you intened to write about.

the real basics:
http://www.pcmech.com/show/network/126/

When it was first introduced and accepted:
http://www.sei.cmu.edu/str/descriptions/clientserver_body.html

Basic Concepts of Client/server Architecture:
http://www.darwinmag.com/read/090103/question11.html

little bit more depth with nice diagrams
http://ipas.ngfl.gov.uk/downloads/pdf/technical/TG09_1-2_clientserv_nwk.pdf
exactly the same thing here but in a rtf format, so you can re-use the diagrams easily:
http://ipas.ngfl.gov.uk/downloads/rtf/technical/TG09_1-2_clientserv_nwk.rtf

Presentation, powerpoint
http://www.cob.sjsu.edu/facstaff/kwan_s/clientserver/index.htm