in the early period after after the known as to and also and Human more than MT and but the not only but also no not with as well as not not The gappy-phrases depend on each other, and the more phrases extracted from human-generated (machine-translated) text are found in a sentence, the more likely the sentence is human-generated (machine-translated).
we compute the feature as where w i is a weight of the i-th phrase, and δ(i, s) is a Kronecker's delta function that takes 1 if the sentence s includes the i-th phrase and takes 0 otherwise.