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The territory that now constitutes Tajikistan was previously home to several ancient cultures, including the city of Sarazm of the Neolithic and the Bronze Age, and was later home to kingdoms ruled by people of different faiths and cultures, including the Oxus civilization, Andronovo culture, Buddhism, Nestorian Christianity, Zoroastrianism, and Manichaeism. The area has been ruled by numerous empires and dynasties, including the Achaemenid Empire, Sassanian Empire, Hephthalite Empire, Samanid Empire, Mongol Empire, Timurid dynasty, and the Russian Empire. As a result of the breakup of the Soviet Union, Tajikistan became an independent nation in 1991. A civil war was fought almost immediately after independence, lasting from 1992 to 1997. Since the end of the war, newly established political stability and foreign aid have allowed the country's economy to grow.

What are some of the empires and dynasties that have also ruled over this land?
Answer: Achaemenid Empire, Sassanian Empire, Hephthalite Empire, Samanid Empire, Mongol Empire, Timurid dynasty, and the Russian Empire
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Lack of political unity within Greece resulted in frequent conflict between Greek states. The most devastating intra-Greek war was the Peloponnesian War (431404 BC), won by Sparta and marking the demise of the Athenian Empire as the leading power in ancient Greece. Both Athens and Sparta were later overshadowed by Thebes and eventually Macedon, with the latter uniting the Greek world in the League of Corinth (also known as the Hellenic League or Greek League) under the guidance of Phillip II, who was elected leader of the first unified Greek state in history.

Who was the first leader of a unified Greece?
Answer: Phillip II
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Canadian bitumen does not differ substantially from oils such as Venezuelan extra-heavy and Mexican heavy oil in chemical composition, and the real difficulty is moving the extremely viscous bitumen through oil pipelines to the refinery. Many modern oil refineries are extremely sophisticated and can process non-upgraded bitumen directly into products such as gasoline, diesel fuel, and refined asphalt without any preprocessing. This is particularly common in areas such as the US Gulf coast, where refineries were designed to process Venezuelan and Mexican oil, and in areas such as the US Midwest where refineries were rebuilt to process heavy oil as domestic light oil production declined. Given the choice, such heavy oil refineries usually prefer to buy bitumen rather than synthetic oil because the cost is lower, and in some cases because they prefer to produce more diesel fuel and less gasoline. By 2015 Canadian production and exports of non-upgraded bitumen exceeded that of synthetic crude oil at over 1.3 million barrels (21010^3 m3) per day, of which about 65% was exported to the United States.

Why do refineries like to buy bitumen instead of synthetic oil?
Answer:
cost is lower