Entanglement of formation for a class of $(2\otimes d)$-dimensional   systems
  Currently the entanglement of formation can be calculated analytically for mixed states in a $(2\otimes2)$-dimensional Hilbert space. For states in higher dimensional Hilbert space a closed formula for quantifying entanglement does not exist. In this regard only entanglement bounds has been found for estimating it. In this work, we find an analytical expression for evaluating the entanglement of formation for bipartite ($2\otimes d$)-dimensional mixed states. 
F. Lastra, C.E. L\'opez, L. Roa and J.C. Retamal
quant-ph