for all pairs of states and in the chart, such that the unit-production relation is non-zero. Then
The first summation is carried out once for each state , whereas the second summation is applied for each choice of Z, but only if is not itself a unit production, i.e., .
Rationale. This increments the equivalent of times, accounting for the infinity of surroundings in which Y can occur if it can be derived through cyclic productions. Note that the computation of is unchanged, since already includes an infinity of cyclically generated subtrees for Y, where appropriate.