SYDNEY, Jan. 8 (Xinhua) -- Women's world No. 4 Coco Gauff rediscovered her best form on Wednesday to ensure the United States' title defence remained on track, while Switzerland also reached the semifinals of the mixed teams United Cup. Gauff won her women's singles match against Maria Sakkari, then played a starring role in the mixed doubles to lead the United States to a 2-1 victory over Greece as quarterfinal action kicked off at Perth's...
