updating documentation

pennylane/fermi/fermionic.py

@@ -326,12 +326,18 @@ def to_mat(self, n_orbitals=None, format="dense", buffer_size=None):
 
     def shift_operator(self, initial_position, final_position):
         r"""Shifts an operator in the FermiWord from ``initial_position`` to ``final_position`` by applying the fermionic anti-commutation relations.
+
             There are four anti-commutator relations:
-            1) a(0)a(1) = -a(1)a(0)
-            2) a⁺(0)a⁺(1) = -a⁺(1)a⁺(0)
-            3) a(0)a⁺(1) = -a⁺(1)a(0)
-            4) a(0)a⁺(0) = 1 - a⁺(0)a(0)
-            See https://en.wikipedia.org/wiki/Creation_and_annihilation_operators#Creation_and_annihilation_operators_in_quantum_field_theories for more information.
+
+            .. math::
+
+                a_0 a_1 = -a_1 a_0
+                a^{\dagger}_0 a^{\dagger}_1 = -a^{\dagger}_1 a^{\dagger}_0
+                a_0 a^{\dagger}_1 = -a^{\dagger}_1 a_0
+                a_0 a^{\dagger}_0 = 1 - a^{\dagger}_0 a_0
+
+
+            For more details see `Wikipedia <https://en.wikipedia.org/wiki/Creation_and_annihilation_operators#Creation_and_annihilation_operators_in_quantum_field_theories>`.
 
 
         Args: