Comment (by Roland Haas):

The ExternalLibraries are kept as git repositories on github:

https://github.com/EinsteinToolkit?q=External&type=&language=

finds them.

Eg for FFTW3 it would be: https://github.com/EinsteinToolkit/ExternalLibraries-FFTW3 and the skeleton documentation.tex file (that they are all missing) is the doc/ThornGuide/template.tex file in the main Cactus repo https://bitbucket.org/cactuscode/cactus/src/master/doc/ThornGuide/template.tex

--
Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2428/possible-issue-between-externallibraries