sentences:  Many have since been the subject of a feature in "Doctor Who Magazine", or other professional periodicals or books devoted to the television show.Such serials exist during the tenure of each of the previous twelve incarnations of the Doctor.The reasons for the serials being incomplete include strike action (which caused the partially filmed "Shada" to be abandoned), actors leaving roles ("The Final Game", which was cancelled after Roger Delgado's death), and the series being put on hiatus twice—once in 1985, and again in 1989—causing the serials planned for the following series to be shelved.