Remove a commented out token that is a left-over from previous commits.
Minor simpifications.
Escape underscores so that they can be input into the latex manual without further change.
Escape underscores so that they can be input into the latex manual without further change.
Greatly extend the documentation of the 'simple' material model to explicitly say what it actually does.
Undo two parts of previous changes since there is apparently a script
(update_parameters.sh) that does these transformations automatically.
Merge pull request #21 from bangerth/fixes

Document the simple material model (and other related and assorted fixes).