Cirac, J. Ignacio Theory, Max Planck Institute of Quantum Optics, Max Planck Society;
Vidal, G., Dür, W., & Cirac, J. I. (2002). Entanglement cost of bipartite mixed states. Physical Review Letters, 89(2):, 027901. Retrieved from http://link.aps.org/abstract/PRL/v89/e027901.