  The gluon recombination functions in the twist-4 QCD evolution equations are
studied at the leading logarithmic approximation using both the covariant and
non-covariant methods. We justify that the infrared singularities in the
twist-4 coefficient functions impede us to simply separate the QCD evolution
kernels from the coefficient functions at the equivalent particle
approximation. In particulary, we point out that the gluon recombination
functions in the GLR-MQ evolution equation are unavailable. The methods
avoiding the IR divergences are discussed, which can be used in the derivations
of the evolution kernels and coefficient functions at the higher twist level.
