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Gosliner, T.M., Behrens, D.W. & Williams, G.C. (1997) Coral Reef Animals of the Indo-Pacific. 314pp.
Monterey, California: Sea Challengers.
Wikipedia points out at the Pseudobiceros hancockanus site that it "is very similar in appearance to Pseudobiceros uniarborensis, although the margin of P. uniarborensis is translucent gray with a white line only on the outside, while the margin of P. hancockanus is pure bright white."
Looking at the pictures of Pseudobiceros uniarbonensis at the Wild Singapore website, I am pretty sure the above specimens are the same species.