The paper by L. Henderson and V. Vedral discusses the problem of separating total correlations in a bipartite quantum state into classical and quantum parts. They propose a measure of classical correlations and explore its properties. The authors review existing measures of entanglement and total correlations, including the Shannon entropy, relative entropy, mutual information, Von Neumann entropy, and entanglement of formation. They define a measure of classical correlations, denoted as \( C_B(\rho_{AB}) \) or \( C_A(\rho_{AB}) \), which satisfies four key properties: zero for product states, invariance under local unitary transformations, non-increase under local operations, and equality for pure states. The measure is shown to be non-increasing under local operations, a crucial property. The paper also examines the relationships between classical, total, and entangled correlations in various quantum states, such as Bell states and Werner states, and raises several open questions about the general relations between these measures. The authors suggest that a better understanding of these correlations could aid in the manipulation of entanglement and classical information in quantum protocols.The paper by L. Henderson and V. Vedral discusses the problem of separating total correlations in a bipartite quantum state into classical and quantum parts. They propose a measure of classical correlations and explore its properties. The authors review existing measures of entanglement and total correlations, including the Shannon entropy, relative entropy, mutual information, Von Neumann entropy, and entanglement of formation. They define a measure of classical correlations, denoted as \( C_B(\rho_{AB}) \) or \( C_A(\rho_{AB}) \), which satisfies four key properties: zero for product states, invariance under local unitary transformations, non-increase under local operations, and equality for pure states. The measure is shown to be non-increasing under local operations, a crucial property. The paper also examines the relationships between classical, total, and entangled correlations in various quantum states, such as Bell states and Werner states, and raises several open questions about the general relations between these measures. The authors suggest that a better understanding of these correlations could aid in the manipulation of entanglement and classical information in quantum protocols.