Interesting article in today's NY Times arts section (by Edward Rothstein) - new book by anthropologist Mary Douglas, Thinking in Circles, on role of ring-structure in ancient literature (Bible, Homer).
Not a new discovery. Alastair Fowler devoted several books (decades ago) to ring-structure and other numerical-geometrical patterns in poetry. But it looks like Mary Douglas has expanded the field.
(Fowler had a big impact on my own writing - ring-design became basic aspect of composition, after I read his work about 15 years ago.)