The index entry for clifford::get_metric() did not work, change it to get_metric().
Signed-off-by: Vladimir V. Kisil <kisilv@maths.leeds.ac.uk>
Note that the call @code{clifford_unit(mu, minkmetric())} creates
something very close to @code{dirac_gamma(mu)}, although
@code{dirac_gamma} have more efficient simplification mechanism.
-@cindex @code{clifford::get_metric()}
+@cindex @code{get_metric()}
The method @code{clifford::get_metric()} returns a metric defining this
Clifford number.