  We describe a new method of reduced Google matrix which allows to establish
direct and hidden links between a subset of nodes of a large directed network.
This approach uses parallels with quantum scattering theory, developed for
processes in nuclear and mesoscopic physics and quantum chaos. The method is
applied to the Wikipedia networks in different language editions analyzing
several groups of political leaders of USA, UK, Germany, France, Russia and
G20. We demonstrate that this approach allows to recover reliably direct and
hidden links among political leaders. We argue that the reduced Google matrix
method can form the mathematical basis for studies in social and political
sciences analyzing Leader-Members eXchange (LMX).
