Intrinsic Charm Contribution to $J/\psi$ Plus Open Charm Associated   Production at High Energies
  We present the results of a calculation of the intrinsic charm quark contribution to $J/\psi$ plus open charm associated production at large transverse momentum in hadron collisions at high energies.   It is shown that the value of the cross section for such process and its energy dependence are significantly determined by the choice of charm quark distribution function. We find that intrinsic charm contribution to inclusive $J/\psi$ hadroproduction is about 1\% of the total contribution of all mechanisms. 
A.P Martynenko and V.A. Saleev