. . "Soviet Union" . . "Rusia" . . "The challenge of the left opposition, 1923-25"@en . "The challenge of the left opposition, 1923-25" . . . . . . . "History"@en . . . . . . "The challenge of the left opposition (1923-25)"@en . "The challenge of the Left Opposition (1923-25)" . . . . "The challenge of the left opposition : 1923-25" . .