diff --git a/doc/source/user_manual/modules/model.rst b/doc/source/user_manual/modules/model.rst
index beb8978..3d4171b 100644
--- a/doc/source/user_manual/modules/model.rst
+++ b/doc/source/user_manual/modules/model.rst
@@ -198,6 +198,31 @@ The XML format for specifying a broken power law is:
+
+Gaussian
+^^^^^^^^
+
+The ``GModelSpectralGauss`` class implements the gaussian function
+
+.. math::
+ \frac{dN}{dE} = \frac{N_0}{\sqrt{2\pi}\sigma}\exp(\frac{-(E-E_bar)^2}{2 \sigma^2})
+
+where the parameters in the XML definition have the following mappings:
+
+* :math:`N_0` = ``Prefactor``
+* :math:`E_bar` = ``Mean Energy``
+* :math:`sigma` = ``Energy Standard Deviation``
+
+The XML format for specifying a power law is:
+
+.. code-block:: xml
+
+
+
+
+
+
+
Node function
^^^^^^^^^^^^^