content_image/310428.jpg content_image/310435.jpg content_image/310434.jpg
while for i < l ≤ N , 

<img src='content_image/310428.jpg'>

<img src='content_image/310435.jpg'>

The first term of the sum in each line of (26) and (27) can split into sum over adjacent points again, for example, the first term in the first line of (26) can be expressed as 

<img src='content_image/310434.jpg'>

For a given r , we have inserted a gluon corresponding to ( N + 1)$_{h}$ between r and r + 1, then (28) insert a gluon corresponding to ( N + 2)$_{h}$ at a position between 1 and r . The second term in the first line of (26) insert an gluon corresponding to ( N + 2)$_{h}$ between r and the gluon corresponding to ( N +1)$_{h}$. Thus the first line of (26) just insert a gluon corresponding to ( N + 2)$_{h}$ at the positions between 1 and the gluon corresponding to ( N + 1)$_{h}$, where the gluon corresponding to ( N + 1)$_{h}$ have been inserted at positions between 1 and l . In a same 

