Update terms_and_model.rst

fix the syntax to correctly reference the "Introduction" section

docs/source/terms_and_model.rst

@@ -11,7 +11,7 @@ correctly reflecting uncertainty of our understanding at the
 time. Unfortunately, such terms are not readily translatable into an
 unambiguous representation of knowledge.
 
-As discussed in the :ref:'Introduction', categorical variation labels are homophonous, ambiguous, and vague, often all three simultanously.  This poses a great difficulty to the precise representation of categorical variation.  In contrast, **the computational representation of categorical variation concepts requires
+As discussed in the :ref:`Introduction`, categorical variation labels are homophonous, ambiguous, and vague, often all three simultanously.  This poses a great difficulty to the precise representation of categorical variation.  In contrast, **the computational representation of categorical variation concepts requires
 translating precise categorical definitions into information models and
 data structures that may be used in software.** This translation
 should result in a representation of information that is consistent