  The topological classification of a series of frustration-induced spin-gap
phases in the spin-1/2 ferromagnetic--antiferromagnetic alternating Heisenberg
chain with next-nearest-neighbour interaction reported in J. Phys. Soc. Jpn.
82, 064703 (2013) is confirmed using two kinds of entanglement spectra defined
by different divisions of the whole chain. For the numerical calculation, the
iDMRG method is used. The results are consistent with the valence bond solid
picture proposed in the previous paper.
