Here is a question about this article: The London Underground in England is one of the few networks that uses a four-rail system. The additional rail carries the electrical return that, on third rail and overhead networks, is provided by the running rails. On the London Underground, a top-contact third rail is beside the track, energized at +420v DC, and a top-contact fourth rail is located centrally between the running rails at −210v DC, which combine to provide a traction voltage of 630v DC. London Underground is now upgrading its fourth rail system to 750v DC with a positive conductor rail energised to +500v DC and a negative conductor rail energised to -250v DC. However, many older sections in tunnels are still energised to 630v DC. The same system was used for Milan's earliest underground line, Milan Metro's line 1, whose more recent lines use an overhead catenary or a third rail.
What is the answer to this question: Where was the system similar to London Underground used as well?
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So... Milan


Here is a question about this article: Writings in Estonian became significant only in the 19th century with the spread of the ideas of the Age of Enlightenment, during the Estophile Enlightenment Period (1750–1840). Although Baltic Germans at large regarded the future of Estonians as being a fusion with themselves, the Estophile educated class admired the ancient culture of the Estonians and their era of freedom before the conquests by Danes and Germans in the 13th century.
What is the answer to this question: Who conquered the ancient Estonians?
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So... Danes and Germans


Here is a question about this article: Beyond combat flight crew personnel, perhaps the most dangerous USAF jobs are Explosive Ordnance Disposal (EOD), Combat rescue officer, Pararescue, Security Forces, Combat Control, Combat Weather, Tactical Air Control Party, and AFOSI agents, who deploy with infantry and special operations units who disarm bombs, rescue downed or isolated personnel, call in air strikes and set up landing zones in forward locations. Most of these are enlisted positions augmented by a smaller number of commissioned officers. Other career fields that have seen increasing exposure to combat include civil engineers, vehicle operators, and Air Force Office of Special Investigations (AFOSI) personnel.
What is the answer to this question: What do some of these special missions in the USAF who deploy with the infantry do?
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So...
rescue downed or isolated personnel