2(1-z)(-1) k+11 1 3 2 3 2 4 '' 1 2 2 2 ' 1 ) 2 (1 ! ) 2 ( ) 2 (1 2! | (1 ) 2! | (1 ) 2(1 )( 1) ) 2 ( (1 ) 1 | (1 ) 1 ) 2 ( + = = = = - = - - = - - - - = - = - = k k i z i z i z i i k f z z i i z f z z i f