  In a recent paper [arXiv:1106.0166], boundary contributions in BCFW recursion
relations have been related to roots of amplitudes. In this paper, we make
several analyses regarding to this problem. Firstly, we use different ways to
re-derive boundary BCFW recursion relations given in [arXiv:1106.0166].
Secondly, we generalize factorization limits to z-dependent ones, where
information of roots is more transparent. Then, we demon- strate our analysis
with several examples. In general, relations from factorization limits cannot
guarantee to find explicit expressions for roots.
