Here are a few flexagon articles and references:

Dmitry Vasilyev was kind enough to send me a scan of this facinating article on tetra-flexagons that was published about 1970 in the Russian Federation journal:  Nauka i Zhizn (Science and Life, Russian: Наука и жизнь).  (Click for full scan of pages)

  Page 1  Page 2  Page 3
 Page 1 Article  Page 2  Page 3

 

Flexagon article links: