Question: When did East Germany and the country where Ricki Osterthun is a citizen unite?

full_context: Document 1: Rainer Rauffmann: After having played mainly for modest clubs in his country of birth, Germany, he revived his career in Cyprus where he played with success for Omonia, eventually representing the Cypriot national team despite having already reached his 30s.
Document 2: Berlin Wall: In 1989 a series of revolutions in nearby Eastern Bloc countries -- Poland and Hungary in particular -- caused a chain reaction in East Germany that ultimately resulted in the demise of the Wall. After several weeks of civil unrest, the East German government announced on 9 November 1989 that all GDR citizens could visit West Germany and West Berlin. Crowds of East Germans crossed and climbed onto the Wall, joined by West Germans on the other side in a celebratory atmosphere. Over the next few weeks, euphoric people and souvenir hunters chipped away parts of the Wall; the governments later used industrial equipment to remove most of what was left. The ``fall of the Berlin Wall ''paved the way for German reunification, which formally took place on 3 October 1990.
Document 3: Hans-Georg von der Osten: Leutnant Hans-Georg von der Osten began his career as a World War I flying ace credited with five aerial victories. He later rose to command of all Luftwaffe bases in Germany, during World War II.
Document 4: Germany: After Germany surrendered, the Allies partitioned Berlin and Germany's remaining territory into four military occupation zones. The western sectors, controlled by France, the United Kingdom, and the United States, were merged on 23 May 1949 to form the Federal Republic of Germany (Bundesrepublik Deutschland); on 7 October 1949, the Soviet Zone became the German Democratic Republic (Deutsche Demokratische Republik). They were informally known as West Germany and East Germany. East Germany selected East Berlin as its capital, while West Germany chose Bonn as a provisional capital, to emphasize its stance that the two - state solution was an artificial and temporary status quo.
Document 5: Ricki Osterthun: Ricki Osterthun (born 2 May 1964, in Hamburg) is a former tennis player from West Germany, who won one single title (1985, Hilversum) during his professional career.
Document 6: Unification of Germany: The unification of Germany into a politically and administratively integrated nation state officially occurred on 18 January 1871, in the Hall of Mirrors at the Palace of Versailles in France. Princes of the German states, excluding Austria, gathered there to proclaim Wilhelm I of Prussia as German Emperor after the French capitulation in the Franco - Prussian War. Unofficially, the de facto transition of most of the German - speaking populations into a federated organization of states had been developing for some time through alliances formal and informal between princely rulers -- but in fits and starts; self - interests of the various parties hampered the process over nearly a century of autocratic experimentation, beginning in the era of the Napoleonic Wars, which saw the dissolution of the Holy Roman Empire of the German Nation (1806), and the subsequent rise of German nationalism.
Document 7: German reunification: The German reunification (German: Deutsche Wiedervereinigung) was the process in 1990 in which the German Democratic Republic (GDR / DDR / East Germany) joined the Federal Republic of Germany (FRG / West Germany) to form the reunited nation of Germany, and when Berlin reunited into a single city, as provided by its then Grundgesetz constitution Article 23. The end of the unification process is officially referred to as German unity (German: Deutsche Einheit), celebrated on 3 October (German Unity Day) (German: Tag der deutschen Einheit). Following German reunification, Berlin was once again designated as the capital of united Germany.
Document 8: Hernán Gumy: Hernán Gumy (born 5 March 1972) is a former tennis player from Argentina, who turned professional in 1991. He represented his native country at the 1996 Summer Olympics in Atlanta, Georgia, where he was defeated in the first round by Venezuela's Nicolas Pereira. Gumy made two finals in his career; both of them ATP 250s on clay in 1996. He won Santiago, Chile (his final tournament of 1996) by beating the Spanish World No. 15 Félix Mantilla in a tough three-setter: in the semi-finals, and the Chilean world number 11 Marcelo Ríos in the final 6-4, 7-5. He lost the other final he was in, in Oporto, Portugal to Spain's Félix Mantilla despite winning the first set.
Document 9: Ralf Reichenbach: Ralf Reichenbach (31 July 1950, in Wiesbaden – 12 February 1998, in Berlin) was a German shot putter. He represented West Germany and competed for the club OSC Berlin and LG Süd Berlin during his active career. He competed in the men's shot put at the 1972 Summer Olympics and the 1976 Summer Olympics.
Document 10: States of Germany: After the Nazi Party seized power in January 1933, the Länder increasingly lost importance. They became administrative regions of a centralised country. Three changes are of particular note: on January 1, 1934, Mecklenburg-Schwerin was united with the neighbouring Mecklenburg-Strelitz; and, by the Greater Hamburg Act (Groß-Hamburg-Gesetz), from April 1, 1937, the area of the city-state was extended, while Lübeck lost its independence and became part of the Prussian province of Schleswig-Holstein.
Document 11: History of Germany (1945–1990): The intended governing body of Germany was called the Allied Control Council. The commanders - in - chief exercised supreme authority in their respective zones and acted in concert on questions affecting the whole country. Berlin, which lay in the Soviet (eastern) sector, was also divided into four sectors with the Western sectors later becoming West Berlin and the Soviet sector becoming East Berlin, capital of East Germany.
Document 12: Claudia Österheld: Claudia Österheld (born 8 December 1968 in Kassel) is a West Germany sprint canoer who competed in the late 1980s. At the 1988 Summer Olympics in Seoul, she finished fifth in the K-4 500 m event while being eliminated in the semifinals of the K-2 500 m event.
Document 13: Dresden: Since German reunification in 1990 Dresden is again a cultural, educational and political centre of Germany and Europe. The Dresden University of Technology is one of the 10 largest universities in Germany and part of the German Universities Excellence Initiative. The economy of Dresden and its agglomeration is one of the most dynamic in Germany and ranks first in Saxony.  It is dominated by high-tech branches, often called “Silicon Saxony”. The city is also one of the most visited in Germany with 4.3 million overnight stays per year. The royal buildings are among the most impressive buildings in Europe. Main sights are also the nearby National Park of Saxon Switzerland, the Ore Mountains and the countryside around Elbe Valley and Moritzburg Castle. The most prominent building in the city of Dresden is the Frauenkirche. Built in the 18th century, the church was destroyed during World War II. The remaining ruins were left for 50 years as a war memorial, before being rebuilt between 1994 and 2005.
Document 14: Territorial evolution of Germany: The territorial changes of Germany include all changes in the borders and territory of Germany from its formation in 1871 to the present. Modern Germany was formed in 1871 when Otto von Bismarck unified most of the German states, with the notable exception of Austria, into the German Empire. After the First World War, Germany lost about 10% of its territory to its neighbours and the Weimar Republic was formed. This republic included territories to the east of today's German borders.
Document 15: Rick Rickert: Rick Rickert (born February 11, 1983) is an American former professional basketball player. He is a 2001 graduate of Duluth East High School where he was a basketball star and highly recruited college prospect. He was named 2001 Minnesota Mr. Basketball.
ground_truth: 1990
sub_queries: Ricki Osterthun >> country of citizenship Answer: West Germany
when did east germany and West Germany unite Answer: 1990