Fragmentation of bottom quarks in top quark decay

We review the main aspects of the fragmentation of bottom quarks in top quark decay. The NLO b-quark energy spectrum presents large mass logarithms ln(m_t^2/m_b^2), which can be resummed by the use of the approach of perturbative fragmentation functions. Large soft contributions in both coefficient function and initial condition of the perturbative fragmentation function have been resummed as well. Results on the energy distribution of b quarks and b-flavoured hadrons are finally presented in both x and moment spaces.