(4.1.21) Teale and Helgaker : Recently, we addressed the issue of attempting to solve the Euler-Lagrange equation of orbitalfree DFT in the all-electron context. Using a second-order optimization method based on the trust-region image method (TRIM), we could robustly solve the equation for many systems by simultaneously optimizing the density and the chemical potential in the saddle function (ρ, µ) → F[ρ] + (v(r)µ)ρ(r) dr + µN. An interesting finding is that more complicated GGA-type functionals often show an erroneous nonconvex behaviour for the model Ts [ρ] (where tilde indicates an approximate quantity). As a result, many solutions (rather than one solution) to the Euler-Lagrange problem with a given particle number N are found. Since T s [ρ] is the noninteracting limit of F[ρ] and since both functionals are convex with respect to the density variations, it would be interesting to explore techniques to impose convexity on approximate Ts [ρ] and Orbital-free approaches can be valuable not only in static DFT but also in time-dependent DFT. I would like to point out the existence of an orbital-free quantumcontinuum-mechanics (QCM) approach, 571-573 which offers an alternative to the time-dependent Kohn-Sham approach in calculating the dynamics of interacting electronic systems. This approach is based on the observation that the density ρ(r,t) and current j(r,t) of the many-body system obey the exact equations of motion and