In 2001, the LA Times printed an article titled "The Lily Porridge of the Stamp
Makers". This article raised curiosity about the origins of the information
presented, and one reader contacted the author inquiring about the
sources.  Here is the reply that was forwarded to us.
  Here's the response I got from Charles Perry on the sources for his
  article:
  The lily root information, which refers to the traditional and not the
  present-day diet of the Tuva, comes from "The Peoples of Siberia," edited by
  M.G. Levin and L.P. Potapov, published by the University of Chicago Press in 1964; it is a translation of
  "Narody Sibiri," published by the Russian Academy of Science, Moscow, in 1956.
  The chapter on the Tuvas is on pp. 380-433. The Chinese reference to
  the Dubo as lily-root eaters is on p. 382; the discussion of lily root in
  traditional diet is on p. 394.  This book might be hard to find but some of your Tuvaphiles will know
  "Tuvan Manual," the grammar and chrestomathy of Tuvan published by the
  Ural-Altaic center at the University of Indiana in the early '70s.  The
  article on the Tuvas from the Levin/Potapov book is reprinted there. In fact, "Tuvan Manual" is the first place I read it.