In this task, you're given a passage, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both passage and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the passage or linked information.

Let me give you an example: Passage: The group was occasionally diverted from strategic missions to carry out air support and interdiction missions. It supported Operation Overlord, the invasion of Normandy by attacking transportation targets, including bridges, along with airfields and strong points in France. On D Day, the squadron and the rest of the 446th Group led the first heavy bomber mission of the day. The 446th aided ground forces at Caen and Saint-Lô during July by hitting bridges, gun batteries, and enemy troops. During Operation Market Garden, the attempt to seize a bridgehead across the Rhine in the Netherlands, the 704th dropped supplies to allied troops near Nijmegen. It struck lines of communications during the Battle of the Bulge. During Operation Varsity in March 1945, it supplied ground and airborne troops near Wesel. The squadron flew its last combat mission on 25 April 1945 against Salzburg, Austria. The group had flown 273 missions and had lost 58 aircraft during the war,
. Link Information: Operation Market Garden was a failed World War II military operation fought in the Netherlands from 17 to 25 September 1944. Answer: from 17 to 25 September 1944
The answer to this example can be: When did the operation during which the 704th dropped supplies to allied troops near Nijmegen begin?
Here is why: The passage describes the 704th's actions during Operation Market Garden, and the answer specifies when the operation happened.

OK. solve this:
Passage: A native of the Ukrainian port city of Odessa (a part of the Soviet Union until 1991), Izold Pustõlnik graduated cum laude from Odessa University in 1960 and received his Ph.D. from the University of Tartu in 1969 and his D.Sc. from Saint Petersburg State University in 1994. From the age of 27 in 1965 until his death forty-three years later, he was on the staff of Tartu Observatory where, as a research associate (promoted to senior research associate in 2000), he worked on the physics of close binary systems, theory of stellar atmospheres, interstellar medium, archaeoastronomy and history of astronomy. He was also a member of the International Astronomical Union, European Astronomical Society, Euroscience, Society for European Astronomy in Culture (SEAC) and served on the Board of Euro-Asian Astronomical Society and the Advisory Board of Astronomical and Astrophysical Transactions. 
 Link Information: The Tartu Observatory () is the largest astronomical observatory in Estonia Answer: Estonia
Answer:
What country is the observatory located in that Pustõlnik was on the staff of for forty-three years?