Collated results at the WTA Bad Homburg grass court tournament on Friday (x denotes seeded player): Quarter-finals Petra Kvitova (CZE x1) bt Nadia Podoroska (ARG x5) 6-3, 7-6 (12/10) Angelique Kerber (GER x4) bt Amanda Anisimova (USA) 2-6, 6-3, 6-3 Katerina Siniakova (CZE) bt Laura Siegemund (GER x8) 7-5, 6-4 Semi-finals Katerina Siniakova (CZE) bt Sara Sorribes (ESP x7) 6-2, 6-4 Angelique Kerber (GER x4) bt Petra Kvitova (CZE x1) bt 3-6, 6-4, 7-6 (7/3) afp