In "2.2. How to translate" on the "Translation" page of http://www.lyx.org/, there is a description:
> For example, the German example documents (which still go in the lib/examples directory) > are de_beispiel_roh.lyx and de_beispiel_gelyxt.lyx. But in recent versions of LyX, lib/examples page contains subdirectories for each languages and the prefix, say de_*, is not required. Koji
