Answer by taking a quote from the following article:

Stefanie Graf was born on 14 June 1969, in Mannheim, Baden-Wurttemberg, West Germany, to Heidi Schalk and Peter Graf (18 June 1938 - 30 November 2013), a car and insurance salesman. When she was nine years old her family moved to the neighbouring town of Bruhl. She has a younger brother Michael. Graf was introduced to tennis by her father, an aspiring tennis coach, who taught his three-year-old daughter how to swing a wooden racket in the family's living room.

In late 1999 and early 2000, as part of her Farewell Tour, Graf played a series of exhibition matches against former rivals in New Zealand, Japan, Spain, Germany and South Africa. She played Jelena Dokic in Christchurch, New Zealand, Amanda Coetzer in Durban, South Africa, and her former rival Arantxa Sanchez Vicario in Zaragoza, Spain. It was Graf and Sanchez Vicario's first head-to-head meeting since 1996. In February 2000, Graf played against Kimiko Date at Nagoya Rainbow Hall in Tokyo, winning in three sets. In September 2004, Graf dispatched her former doubles partner Gabriela Sabatini in straight sets, in an exhibition match played in Berlin, Germany. She was also in Berlin to host a charity gala, as well as inaugurating a tennis stadium renamed the "Steffi Graf Stadion". Proceeds from her match against Sabatini went to Graf's foundation, "Children for Tomorrow".  In July 2005, Graf competed in one tie of World Team Tennis (WTT) on the Houston Wranglers team. She was beaten in two out of three matches, with each match being one set. Graf lost her singles match to Elena Likhovtseva 5-4. She teamed with Ansley Cargill in women's doubles against Anna Kournikova and Likhovtseva but lost 5-2. She was successful, however, in the mixed doubles match. Graf completely ruled out a return to professional tennis. In October, Graf defeated Sabatini in an exhibition match in Mannheim, Germany, winning both of their sets. Like the exhibition match the previous year against Sabatini, proceeds went to "Children for Tomorrow".  In 2008 Graf lost an exhibition match against Kimiko Date at Ariake Colosseum in Tokyo. As part of the event, billed as "Dream Match 2008", she defeated Martina Navratilova in a one-set affair 8-7, with Graf winning a tiebreaker 10-5. It was the first time in 14 years Graf had played Navratilova. Graf played a singles exhibition match against Kim Clijsters and a mixed doubles exhibition alongside husband Andre Agassi against Tim Henman and Clijsters as part of a test event and celebration for the newly installed roof over Wimbledon's Centre Court in 2009. She lost a lengthy one-set singles match to Clijsters and also the mixed doubles.  In 2010, Graf participated in the WTT Smash Hits exhibition in Washington, D.C. to support the Elton John AIDS Foundation. She and Agassi, her husband, were on Team Elton John, which competed against Team Billie Jean King. Graf played in the celebrity doubles, women's doubles, and mixed doubles before straining her left calf muscle and being replaced by Anna Kournikova.

What year did these start?
early 2000,