Comment on ``Dynamics of open quantum systems initially entangled with   environment: Beyond the Kraus representation'' [PRA 64, 062106 (2001)]
  We correct a mistake in a result reported in [PRA 64, 062106 (2001)], where it is rightfully argued that initial correlations between a system and its environment may render the system reduced dynamics not completely positive. We prove how not only these initial correlations but also the specific joint dynamics does play a significant role in the question of the complete positivy of the reduced dynamics. 
D. Salgado and J.L. Sanchez-Gomez