Complex sentence: Bergson was unable to offer evidence of Nasser's alleged statement and acknowledged that, after thorough research, he had been unable to find any statement by a responsible Arab leader that could be described as genocidal.
Split into simpler sentences: Bergson was unable to offer evidence of Nasser's alleged statement. Bergson acknowledged that, after thorough research, he had been unable to find any statement by a responsible Arab leader which could be described as genocidal.