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In page Doctor Who:

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Some episodes have been returned to the BBC from the archives of other countries that bought prints for broadcast[6] or by private individuals who acquired them by various means.[7] Early colour videotape recordings made off-air by fans have also been retrieved,[8] as well as excerpts filmed from the television screen onto 8 mm cine film[9] and clips that were shown on other programmes.[10] Audio versions of all lost episodes exist from home viewers who made tape recordings of the show.[11] Short clips from every story with the exception of Marco Polo (1964), "Mission to the Unknown" (1965) and The Massacre (1966) also exist.[citation needed]