An Analytical Expression for the Non-Singlet Structure Functions at   Small $x$ in the Double Logarithmic Approximation
  A simple analytic expression for the non-singlet structure function $f_{NS}$ is given. The expression is derived from the result of Ref. [1] obtained by low $x$ resummation of the quark ladder diagrams in the double logarithmic approximation of perturbative QCD. 
Michael Lublinsky