In this paper the revised Kajantie-Byckling approach and improved phase space
sampling techniques for the massive multi-particle final states are presented.
The application of the developed procedures to the processes representative for
LHC physics indicates the possibility of a substantial simplification of
multi-particle phase space sampling while retaining a respectable weight
variance reduction and unweighing efficiencies in the event generation process.Comment: Minor stilistic changes, submitted to EPJ