Virtual PBX vs. Hosted PBX Vs On Premise PBX

http://www.voip-info.org/wiki/view/Hosted+PBX+Vs+On+Premise+PBX
http://www.voip-info.org/wiki/view/Hosted+PBX+vs+Virtual+PBX
http://www.voip-info.org/wiki/view/Hosted+PBX
http://www.voip-info.org/wiki/view/Virtual+PBX
http://technews.tmcnet.com/channels/business-voip-providers/articles/330833-cloud-pbx-vs-hosted-pbx-whats-real-difference.htm

[Note] Virtual PBX