sentence1: clark et al use the results of one pos tagger on unannotated data to inform the training of another tagger in a semi-supervised setting using a co-training routine with a markov model tagger and a maximum entropy tagger .
sentence2: for pos tagging , clark et al used the results of one pos tagger on unannotated data to inform the training of another tagger in a semisupervised setting using a co-training routine with a markov model tagger and a maximum entropy tagger .