1. A method for enhancing a performance of a first classifier used for classifying a first subset of documents written in a first language, the method comprising: a) providing a second subset of documents written in a second language different than the first language, said second subset including substantially the same content as the first subset; b) running the first classifier over the first subset to generate a first classification; c) running a second classifier over the second subset to generate a second classification; d) reducing a training cost between the first and second classifications, said reducing comprises repeating steps b) and c) wherein each classifier updates its own classification in view of the classification generated by the other classifier until the training cost is set to a minimum; and e) outputting at least one of said first classification and said first classifier.