minor fix

Author: Dario Coscia

docs/source/_rst/tutorial1/tutorial.rst

@@ -82,12 +82,11 @@ time domain where we want the solution.
 Summarizing, in PINA we can initialize a problem with a class which is
 inherited from three base classes: ``SpatialProblem``,
 ``TimeDependentProblem``, ``ParametricProblem``, depending on the type
-of problem we are considering. For reference: \* ``SpatialProblem``
-:math:`\rightarrow` spatial variable(s) presented in the differential
-equation \* ``TimeDependentProblem`` :math:`\rightarrow` time
-variable(s) presented in the differential equation \*
-``ParametricProblem`` :math:`\rightarrow` parameter(s) presented in the
-differential equation
+of problem we are considering. For reference:
+
+* ``SpatialProblem`` :math:`\rightarrow` spatial variable(s) presented in the differential equation 
+* ``TimeDependentProblem`` :math:`\rightarrow` time variable(s) presented in the differential equation 
+* ``ParametricProblem`` :math:`\rightarrow` parameter(s) presented in the differential equation
 
 Write the problem class
 ~~~~~~~~~~~~~~~~~~~~~~~