Complex sentence: Its article refers to a journalist named "KGB officer", who claims he took part in the construction of a large underground facility in Ramenki, whereby construction began in the mid- 1960s and was complete by mid- 1970.
Split into simpler sentences: Its article refers to a journalist named "KGB officer", who claims he took part in the construction of a large underground facility in Ramenki. It was claimed construction began in the mid- 1960s and was complete by mid- 1970.