Nonetheless, several properties distinguish our corpus of peer reviews from other types of reviews: 1) The helpfulness of our peer reviews is directly rated using a discrete scale from one to five instead of being defined as a function of binary votes (e.g. the percentage of "helpful" votes<cite> (Kim et al., 2006)</cite> ); 2) Peer reviews frequently refer to the related students' papers, thus review analysis needs to take into account paper topics; 3) Within the context of education, peer-review helpfulness often has a writing specific semantics, e.g. improving revision likelihood; 4) In general, peer-review corpora collected from classrooms are of a much smaller size compared to online product reviews.