 Professor Zvi Gitelman ("A Century of Ambivalence") estimated that only in 1918–1919 over 1,200 pogroms took place in Ukraine, thus amounting to the greatest slaughter of Jews in Eastern Europe since 1648.Aleksandr Solzhenitsyn in his book "Two Hundred Years Together" provided additional statistics from research conducted by Nahum Gergel (1887–1931).Gergel counted 1,236 incidents of anti-Jewish violence and estimated that 887 mass pogroms occurred, the remainder being classified as "excesses" not assuming mass proportions.