Fifth seed Angelique Kerber kept alive her Australian Open hopes despite some nervous moments Madison Keys.
Kerber, who celebrates her 25th birthday today, was able to use her greater experience to overcome the 17-year-old American 6-2 7-5.
However Kerber was forced to work hard by Keys, who is one of the bright young hopes of US tennis.
"It was a very tough match because Madison is a great young player," said Kerber. "I was just trying to focus point by point and I'm so happy to win on my birthday."
Kerber will be joined in the fourth round by Li Na after the sixth seed topped 27th-ranked Sorana Cirstea 6-4 6-1.
Ana Ivanovic came out on top of the all-Serbian clash against Jelena Jankovic - with the 13th seed winning 7-5 6-3.
Julia Goerges, the No 18 seed, recovered from a second-set slump to beat Zheng Jie 6-3 1-6 7-5, while there was a minor upset as 19th seed Ekaterina Makarova edged out the No 11-ranked Marion Bartoli 6-7 (7-4) 6-3 6-4.