What is the greatest source of conflict between Armenia and Azerbaijan?

Here are a couple of sites that will be of help. The third site is an in depth analysis.

http://www.fas.org/man/crs/92-109.htm

http://en.wikipedia.org/wiki/Nagorno-Karabakh_War

http://docs.google.com/viewer?a=v&q=cache:t_0Ip27DWuEJ:www.au.af.mil/au/awc/awcgate/crs/ib92109.pdf+conflict+between+Armenia+and+Azerbaijan&hl=en&gl=us&pid=bl&srcid=ADGEESgMdVCSD1CFbmGh_fEy9MmTApC_UrGImu_WQAPcrSAf-jdd8e6TyJH1vgHX_XFz9bHAxk8oY74oHixphOA09BW74_IiuBhT0LA95Y3DjSu3LvIOBQd26DCpPWQK0es-HkO-iS4T&sig=AHIEtbTDcrKuuHNIIIqQq13M-vesEuMXXw