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Williams ( in William Forbes Skene's "Four Ancient Books of Wales" ) , by Robert Graves in "The White Goddess" and by Roger Sherman Loomis , Herbert Pilch , John T . Koch , Marged Haycock , John K . 
<triplet> Four Ancient Books of Wales <subj> William Forbes Skene <obj> author <triplet> The White Goddess <subj> Robert Graves <obj> author