There are two typos in the following section, I quote: ``Given the context passage of each reference, PBC employs Eq 3 to estimate the similarity betwen two references c1 and c2 in articles d1 and d2 respectively. The context passgaes of c1 and c2 are helpful when c1 and c2 are not identical but they are respectively commented by the authors of d1 and d2 with similar words. The similarity falls in the range of [0, 1]."

(Passages, and between)