[Slonopotam845]

http://www.strategypage.com/htmw/hti.../20110804.aspx
From news article:

August 4, 2011: Turkey is considering purchasing Russian (S300) or Chinese (HQ-9) anti-aircraft missile systems. As a result, because Turkey is a NATO member, and Russia and China are not, NATO informed Turkey that if they bought the Russian or Chinese systems, they would no longer be able to receive NATO classified information pertaining to air defense systems. This is because of the risk of Russia or, especially, China gaining access to these data. Moreover, the Russian and Chinese systems are not, understandably, compatible with NATO ones. That problem could be fixed, but it would again raise the issue of China and Russian obtaining classified technical data on NATO air defense systems.