The count of trees containing span i, j is α(i, j) • β(i, j).
equation 1 can be rewritten as On condition that i, j is a span in the parse of e, the probability that i, j has two children i, k and k + 1, j is the probability that i, j is a span in the parse of e and has two children i, k and k + 1, j can be calculated as follows: Since each candidate projected span aligns to one treelet at most, this probability is also the frequency of the candidate projected production related to the three spans.