Question: What 1970 American born tennis player won the 1990 ATP Tour World Championships – Singles?

full_context: Document 1: 1991 ATP Tour World Championships – Singles: Andre Agassi was the defending champion, but Jim Courier defeated him in the semifinal.
Document 2: Boris Becker: Boris Franz Becker (] ; born 22 November 1967) is a German former world No. 1 professional tennis player. He was successful from the start of his career, winning the first of his six major singles titles aged 17. He also won five year-end championships, 13 Masters Series titles, and an Olympic gold medal in doubles. "Tennis" magazine ranked him the 11th best male player of the period 1965–2005.
Document 3: 1985 Wimbledon Championships – Men's Singles: John McEnroe was the defending champion but lost in the quarterfinals to Kevin Curren. Curren also defeated Jimmy Connors in the semifinal and became the first player ever to defeat both Connors and McEnroe in the same Grand Slam tournament.
Document 4: Hicham Arazi: Hicham Arazi (Arabic: هشام أرازي‎ ‎ ; born 19 October 1973) is a former male tennis player from Morocco. He played professionally from 1993 to the end of 2007. The left-hander reached his career-high ATP Tour singles ranking of world No. 22 on November 5, 2001. During his career, Arazi captured one singles title, in Casablanca. "The Moroccan Magician" reached the quarter-finals of the Australian Open twice and the French Open twice. As well as the aforementioned nickname, some tennis analysts called him "The Moroccan McEnroe" due to his talent - he played with incredible touch, and often enjoyed the support of the crowd even when not at home. He led Patrick Rafter, winner of the US Open in 1997 and 1998, two sets to love during the first round of the latter tournament. In the third set he was upset with several line calls, telling umpire Norm Chryst to "get out of here", which sparked the beginning of Arazi's meltdown (and Rafter's comeback). During his career, he notably gained victories over former World No. 1s and Grand Slam champions Roger Federer, Andre Agassi, Yevgeny Kafelnikov, Marat Safin, Lleyton Hewitt, Juan Carlos Ferrero, Carlos Moyá and Jim Courier.
Document 5: 1994 Lipton Championships – Men's Singles: Pete Sampras was the defending champion and won in the final 5–7, 6–3, 6–3 against Andre Agassi.
Document 6: 1991 Wimbledon Championships – Men's Doubles: The Men's Doubles tournament at the 1991 Wimbledon Championships was held from 24 June to 7 July 1991 on the outdoor grass courts at the All England Lawn Tennis Club in the Wimbledon district in London, England. Rick Leach and Jim Pugh were the defending champions, but lost in the first round to Goran Ivanisevic and John McEnroe. John Fitzgerald and Anders Järryd won the title, defeating Javier Frana and Leonardo Lavalle in the final.
Document 7: Stefan Edberg: Stefan Bengt Edberg (] ; born 19 January 1966) is a Swedish former world no. 1 professional tennis player (in both singles and doubles). A major proponent of the serve-and-volley style of tennis, he won six Grand Slam singles titles and three Grand Slam men's doubles titles between 1985 and 1996. He also won the Masters Grand Prix and was a part of the Swedish Davis Cup-winning-team four times. In addition he won four Masters Series titles, four Championship Series titles and the unofficial Olympic tournament 1984, was ranked in the singles top 10 for ten successive years, 9 years in the top 5, and is considered one of the greatest players of his era. Edberg began coaching Roger Federer in January 2014, with this partnership ending in December 2015.
Document 8: Andre Agassi: Andre Kirk Agassi ( ; born April 29, 1970) is an American retired professional tennis player and former World No. 1 who was one of the sport's most dominant players from the early 1990s to the mid-2000s. Generally considered by critics and fellow players to be one of the greatest tennis players of all time, Agassi has been called the greatest service returner in the history of the game. Described by the BBC upon his retirement as "perhaps the biggest worldwide star in the sport's history", Agassi compiled performances that, along with his unorthodox apparel and attitude, saw him cited as one of the most charismatic players in history. As a result, he is credited for helping to revive the popularity of tennis during the 1990s.
Document 9: Pete Sampras career statistics: This is a list of the main career statistics of American former tennis player Pete Sampras. He turned professional in 1988 and his official retirement occurred in August 2003. During his career Sampras won 64 singles titles, including 14 titles at Grand Slam events. He competed in 16 ties for the United States Davis Cup team between 1991 and 2002 and was a member of the cup winning team in 1992 and 1995. Sampras reached the No. 1 ranking on April 12, 1993 and in total held that position for 286 weeks.
Document 10: 1999 Australian Open – Men's Singles: Petr Korda was the defending champion, but he was eliminated in the third round by Todd Martin.<br>Yevgeny Kafelnikov won the title, defeating Thomas Enqvist in the final, 4–6, 6–0, 6–3, 7–6. With this win, Kafelnikov became the first Russian (male or female) to win the Australian Open.
Document 11: Jim Courier: James Spencer Courier Jr. (born August 17, 1970) is an American former World No. 1 professional tennis player. During his career, he won four Grand Slam singles titles, two at the French Open and two at the Australian Open. He holds the record for being the youngest man to have reached the finals of all four Grand Slam singles tournaments, at the age of 22 years and 11 months. He also won five Masters 1000 series titles. Until Novak Djokovic in 2016, Courier was the last man to win both the Australian and French Opens in the same calendar year.
Document 12: 1991 ATP Tour World Championships: The 1991 ATP Tour World Championships (The singles event was also known as the 1991 IBM ATP Tour World Championships whilst the doubles event was also known as the 1991 Standard Bank ATP Tour World Doubles Final for sponsorship reasons) was held in Frankfurt, Germany between November 12 and November 17, 1991.
Document 13: Pete Sampras: Pete Sampras (born August 12, 1971) is a retired American tennis player widely regarded as one of the greatest in the history of the sport. He was a right-handed player with a single-handed backhand and a precise and powerful serve that earned him the nickname "Pistol Pete". His professional career began in 1988 and ended at the 2002 US Open, which he won, defeating rival Andre Agassi in the final.
Document 14: Arthur Ashe: Arthur Robert Ashe Jr. (July 10, 1943 – February 6, 1993) was an American professional tennis player. He won three Grand Slam titles.
Document 15: Ilie Năstase: Ilie "Nasty" Năstase (] , born 19 July 1946) is a Romanian former world No. 1 professional tennis player, one of the world's top players of the 1970s. He was ranked world no. 1 from 23 August 1973 to 2 June 1974.
ground_truth: Andre Kirk Agassi