Question:  Liezel Huber and Arantxa Sánchez Vicario, are both six time Grand Slam title winners of what sport?
Sentence (from "Arantxa Sánchez Vicario"): Aránzazu Isabel María "Arantxa" Sánchez Vicario (] ; born 18 December 1971) is a Spanish former World No. 1 professional tennis player.
Relevant evidence: Yes