DOC: Fix bibtex citation in plot_dipole_orientations.py #8944. (#9144)

tutorials/source-modeling/plot_dipole_orientations.py

@@ -82,9 +82,9 @@
 # While the source space defines the position of the dipoles, the inverse
 # operator defines the possible orientations of them. One of the options is to
 # assign a fixed orientation. Since the neural currents from which MEG and EEG
-# signals originate flows mostly perpendicular to the cortex [1]_, restricting
-# the orientation of the dipoles accordingly places a useful restriction on the
-# source estimate.
+# signals originate flows mostly perpendicular to the cortex
+# :footcite:`HamalainenEtAl1993`, restricting the orientation of the dipoles
+# accordingly places a useful restriction on the source estimate.
 #
 # By specifying ``fixed=True`` when calling
 # :func:`mne.minimum_norm.make_inverse_operator`, the dipole orientations are
@@ -136,11 +136,12 @@
 # source estimate sensitive to the spacing of the dipoles along the cortex,
 # since the curvature of the cortex changes within each ~10 square mm patch.
 # Furthermore, misalignment of the MEG/EEG and MRI coordinate frames is more
-# critical when the source dipole orientations are strictly constrained [2]_.
-# To lift the restriction on the orientation of the dipoles, the inverse
-# operator has the ability to place not one, but three dipoles at each
-# location defined by the source space. These three dipoles are placed
-# orthogonally to form a Cartesian coordinate system. Let's visualize this:
+# critical when the source dipole orientations are strictly constrained
+# :footcite:`LinEtAl2006`. To lift the restriction on the orientation of the
+# dipoles, the inverse operator has the ability to place not one, but three
+# dipoles at each location defined by the source space. These three dipoles are
+# placed orthogonally to form a Cartesian coordinate system. Let's visualize
+# this:
 fig = mne.viz.create_3d_figure(size=(600, 400))
 
 # Plot the cortex
@@ -218,11 +219,4 @@
 ###############################################################################
 # References
 # ----------
-# .. [1] Hämäläinen, M. S., Hari, R., Ilmoniemi, R. J., Knuutila, J., &
-#    Lounasmaa, O. V. "Magnetoencephalography - theory, instrumentation, and
-#    applications to noninvasive studies of the working human brain", Reviews
-#    of Modern Physics, 1993. https://doi.org/10.1103/RevModPhys.65.413
-#
-# .. [2] Lin, F. H., Belliveau, J. W., Dale, A. M., & Hämäläinen, M. S. (2006).
-#    Distributed current estimates using cortical orientation constraints.
-#    Human Brain Mapping, 27(1), 1–13. http://doi.org/10.1002/hbm.20155
+# .. footbibliography::