Inability to find justification of a $k_T$-factorization formula by   following chains of citations
  Fundamental to much work in small-x QCD is a k_T-factorization formula. Normal expectations in theoretical physics are that when such a result is used, citations should be given to where the formula is justified. We demonstrate by examining the chains of citations back from current work that violations of this expectation are widespread, to the extent that following the citation chains, we do not find a proof or other justification of the formula. This shows a substantial deficit in the reproducibility of a phenomenologically important area of research. Since the published formulae differ in normalization, we test them by making a derivation in a simple model that obeys the assumptions that are stated in the literature to be the basis of k_T-factorization in the small-$x$ regime. We find that we disagree with two of the standard normalizations. 
Emil Avsar and John C. Collins
hep-ph