  We show that the entanglement of cost and entanglement of distillation can be
vague when we consider a more general form of entanglement manipulation in
which we collectively deal with not only states of our concern but also other
states. We introduce the most general entanglement manipulation in which the
formation and distillation can be simultaneously performed. We show that in a
certain case entanglement manipulations are reversible with respect to the most
general entanglement manipulation. This broadens our scope of vision on the
irreversibility of entanglement manipulations.
