It should be noted, however, that these DFAs require solution of orbital equations 175 . Note that the approaches discussed above focus on modelling the Hx functional and state-driven correlations. Failure to include DD correlations in ensemble DFAs leads to "DD correlation errors" that are avoided in pure-state DFT. 1. Self-consistent ensemble DFT calculations still lack a welldefined computational protocol (usual or generalized Kohn-Sham schemes, OEP-type algorithms, CASSCF-type orbital optimization techniques, etc). How best to correct the ghostinteraction error at an affordable cost is also an open question. 2. In GOK DFT, 421 one is supposed to know in advance the energy ordering of the excited states, which is far from being straightforward.