{HEAD ~ The time synchronization schemes} based on a Global Positioning System and {TAIL ~ a wide area communication network} can be combined to synchronize the stationary clocks of phasor measurement units of a wide area monitoring system to a central server clock at a Network Control Center of the system 
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{ HEAD ~ The time synchronization schemes } based on a Global Positioning System and { TAIL ~ a wide area communication network } can be combined to synchronize the stationary clocks of phasor measurement units of a wide area monitoring system to a central server clock at a Network Control Center of the system
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