Some writers venture into less predictable plots, which might even seem to be plotless. Some authors complicate the structure of their plots with the use of flashbacks and flash-forwards; with the frame of a story within a story; or with subplots or double plots which means two or more equally important narratives progressing simultaneously. Besides, another unique technique called deliberate ambiguity or open-endedness is a plot feature found in many modern stories. The surprise endings of French author Guy de Maupassant, as in his 1884 story The Necklace, influenced many commercial writers but also some literary ones. At the turn of the century, American author O. Henry became famous for his paradoxical style and surprise endings, such as in A Gift of the Magi.