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In addition, recording and reproducing an HDTV signal was a significant technical challenge in the early years of HDTV (Sony HDVS). Japan remained the only country with successful public broadcasting of analog HDTV, with seven broadcasters sharing a single channel.

How many broadcasters did Japan have sharing a single channel?
Answer: seven
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Many pre-Columbian civilizations established characteristics and hallmarks which included permanent or urban settlements, agriculture, civic and monumental architecture, and complex societal hierarchies. Some of these civilizations had long faded by the time of the first significant European and African arrivals (ca. late 15thearly 16th centuries), and are known only through oral history and through archaeological investigations. Others were contemporary with this period, and are also known from historical accounts of the time. A few, such as the Mayan, Olmec, Mixtec, and Nahua peoples, had their own written records. However, the European colonists of the time worked to eliminate non-Christian beliefs, and Christian pyres destroyed many pre-Columbian written records. Only a few documents remained hidden and survived, leaving contemporary historians with glimpses of ancient culture and knowledge.

What gave today's historians a glimpse of the culture and knowledge of the indigenous civilizations?
Answer: a few documents
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In November 2005, the Polish government opened its Warsaw Treaty archives to the Institute of National Remembrance, who published some 1,300 declassified documents in January 2006. Yet the Polish government reserved publication of 100 documents, pending their military declassification. Eventually, 30 of the reserved 100 documents were published; 70 remained secret, and unpublished. Among the documents published is the Warsaw Treaty's nuclear war plan, Seven Days to the River Rhine a short, swift counter-attack capturing Austria, Denmark, Germany and Netherlands east of River Rhine, using nuclear weapons, in self-defense, after a NATO first strike. The plan originated as a 1979 field training exercise war game, and metamorphosed into official Warsaw Treaty battle doctrine, until the late 1980s which is why the People's Republic of Poland was a nuclear weapons base, first, to 178, then, to 250 tactical-range rockets. Doctrinally, as a Soviet-style (offensive) battle plan, Seven Days to the River Rhine gave commanders few defensive-war strategies for fighting NATO in Warsaw Treaty territory.[citation needed]

How many documents remain classified?
Answer:
70