We can approach this problem using XCOS simulation   
 
 In this simulation   
 
 1)For injecting unit current at bus1 keeping bus2 open circuit,we use a current source of 1 unit which is  
      switched on from t=0 to t=2. During this period we can observe the voltage waveforms of V1 and V2 and 
       compare with the results given in the textbook                                                       
 
 2)For injecting unit current at bus2 keeping bus1 open circuit,we use a current source of 1 unit which is  
      switched on from t=4 to t=6. During this period we can observe the voltage waveforms of V1 and V2 and 
       compare with the results given in the textbook                                                       
 Zbus  =
 
    7.    4.  
    4.    6.