Jelena Jankovic booked her place in the last four of the BNP Paribas Open . Opponent Lesia Tsurenko retired through injury while trailing 6-1 , 4-1 . Serena Williams takes on Flavia Pennetta in the semis on Friday .
Jelena Jankovic booked her place in the last four of the BNP Paribas Open . Opponent Lesia Tsurenko retired through injury while trailing 6-1 , 4-1 . Serena Williams takes on Simona Halep in the semis on Friday .