‘Jos. Riva’ is a mystery. Only one book exists with the name as illustrator, and though the style is not dissimilar to artists like André Collot or Gaston Trilleau there is no reason for those artists to have used a pseudonym. The point after the ‘Jos.’ strongly suggests Joseph or Josef as a first name, and it has been suggested that the creator of these images is the French artist Joseph Riviere (1912–61), who was primarily a sculptor though he did make some good nude drawings; the date of publication of the Riva-illustrated volume would have made him twenty years old at the time.
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