Grand Slam (tennis) ten women have won Career Grand Slams in singles play (rows one and two); among them two men and five women have at least two Career Grand Slams in singles (column three). Since the beginning of the open era, five men (Rod Laver, Andre Agassi, Roger Federer, Rafael Nadal, Novak Djokovic) and six women (Margaret Court, Chris Evert, Martina Navratilova, Steffi Graf, Serena Williams and Maria Sharapova) have achieved this. Several singles players have won three major championships without achieving the Career Grand Slam, grouped by the "missing" Grand Slam tournament: Several doubles players have won three major championships without
International Tennis Federation ITF organizes the Grand Slam events, annual team competitions for men (Davis Cup), women (Fed Cup), and mixed teams (Hopman Cup), as well as tennis and wheelchair tennis events at the Summer Olympic and Paralympic Games on behalf of the International Olympic Committee. The ITF sanctions the Grand Slam tennis tournaments as well as circuits which span age ranges (junior, professional men and women, and seniors) as well as disciplines (wheelchair tennis; beach tennis). In addition to these circuits, the ITF also maintains rankings for juniors, seniors, wheelchair and beach tennis. Duane Williams, an American who lived in Switzerland, is