diff --git a/SOAP/particle_selection/SO_properties.py b/SOAP/particle_selection/SO_properties.py
index 7faaf700..55746315 100644
--- a/SOAP/particle_selection/SO_properties.py
+++ b/SOAP/particle_selection/SO_properties.py
@@ -604,7 +604,7 @@ def spin_parameter(self) -> unyt.unyt_quantity:
         """
         Spin parameter of all particles in the spherical overdensity.
 
-        Computed as in Bullock et al. (2021):
+        Computed as in Bullock et al. (2001):
           lambda = |Ltot| / (sqrt(2) * M * v_max * R)
         """
         if self.Mtotpart == 0:
diff --git a/SOAP/particle_selection/subhalo_properties.py b/SOAP/particle_selection/subhalo_properties.py
index bd2c94cd..cbb68649 100644
--- a/SOAP/particle_selection/subhalo_properties.py
+++ b/SOAP/particle_selection/subhalo_properties.py
@@ -1032,7 +1032,7 @@ def spin_parameter(self) -> unyt.unyt_quantity:
         """
         Spin parameter of all particles in the subhalo.
 
-        Computed as in Bullock et al. (2021):
+        Computed as in Bullock et al. (2001):
           lambda = |Ltot| / (sqrt(2) * M * v_max * R)
 
         Since a subhalo does not have a characteristic radius, R, we instead use
diff --git a/documentation/footnote_spin.tex b/documentation/footnote_spin.tex
index cf2ddc3c..f089562d 100644
--- a/documentation/footnote_spin.tex
+++ b/documentation/footnote_spin.tex
@@ -1,4 +1,4 @@
-\paragraph{$^{$FOOTNOTE_NUMBER$}$The spin parameter}\label{footnote:$FOOTNOTE_NUMBER$} is computed following Bullock et al. (2021):
+\paragraph{$^{$FOOTNOTE_NUMBER$}$The spin parameter}\label{footnote:$FOOTNOTE_NUMBER$} is computed following Bullock et al. (2001):
 
 \begin{equation}
     \lambda{} = \frac{|\vec{L}_{\rm{}tot}|}{\sqrt{2}M v_{\rm{}max} R},