Addendum: Observation of double charm production involving open charm in pp collisions at $ \sqrt{s} $ = 7 TeV

The production of J/ mesons accompanied by open charm hadrons, and of pairs of open charm hadrons in pp collisions at a centre-of-mass energy of 7 TeV has been reported in ref. For all measured production cross-sections the inclusion of charge conjugate processes was implied, so that e.g.,