We now add a citation to arXiv:1303.3493, where this part is explained in more details. The main point of Helmut is that to normalize the JPsi yield it is not mandatory to measure the total open charm cross section, since the relative abundances of the various open charm states do not depend on energy and are the same for elementary or nuclear collisions. Therefore, the rate of J/ψ /open charm, can in good approximation be taken as the rate of J/ψ/D for a specific D-meson state.