Unlike (Larkey and Croft, 1996) we do not merge our classifiers by linear combination, because the RegEx module does not return a scoring consistent with the vector space system.
the combination does not use the RegEx's edit distance, and instead it uses the list returned by the vector space module as a reference list (RL), while the list returned by the regular expression module is used as boosting list (BL), which serves to improve the ranking of terms listed in RL.