Its title was inspired by a poem by John Keats, "La Belle Dame sans Merci", which contained the lines "The sedge is wither'd from the lake, And no birds sing." "Silent Spring" was initially suggested as a title for the chapter on birds. By August 1961, Carson agreed to the suggestion of her literary agent Marie Rodell: "Silent Spring" would be a metaphorical title for the entire booksuggesting a bleak future for the whole natural worldrather than a literal chapter title about the absence of birdsong. With Carson's approval, editor Paul Brooks at Houghton Mifflin arranged for illustrations by Louis and Lois Darling, who also designed the cover. The final writing was the first chapter, "A Fable for Tomorrow", which was intended to provide a gentle introduction to a serious topic. By mid-1962, Brooks and Carson had largely finished the editing and were planning to promote the book by sending the manuscript to select individuals for final suggestions. In "Silent Spring", Carson relied on evidence from two New York state organic farmers, Marjorie Spock and Mary Richards, and that of biodynamic farming advocate Ehrenfried Pfeiffer in developing her case against DDT.