  In contrast with entanglement, as measured by concurrence, in general,
quantum discord does not possess the property of monogamy, that is, there is no
tradeoff between the quantum discord shared by a pair of subsystems and the
quantum discord that both of them can share with a third party. Here, we show
that, as far as monogamy is considered, quantum discord of pure states is
equivalent to the entanglement of formation. This result allows one to
analytically prove that none of the pure three-qubit states belonging to the
subclass of W states is monogamous. A suitable physical interpretation of the
meaning of the correlation information as a quantifier of monogamy for the
total information is also given. Finally, we prove that, for rank 2 two-qubit
states, discord and classical correlations are bounded from above by
single-qubit von Neumann entropies.
