diff --git a/cpp/kspace.cpp b/cpp/kspace.cpp
index 1549b2dad869207cbf4482246e92823f64542c09..da64403252ba5d400d59190d18a4c4b46d988655 100644
--- a/cpp/kspace.cpp
+++ b/cpp/kspace.cpp
@@ -338,6 +338,12 @@ void kspace<be, dt>::ball_filter(
  *       \exp(-\frac{(3.54 k \ell)^{122 \ell^{0.0836}}}{2})
  *       \left( 1 + \frac{(k \eta/0.0636)^{3.44}}{1 + (k \eta/ 0.0621)^{3.44}} \right)^{1/2}
  *  \f]
+ *
+ *  Citation:
+ *  Johan Meyers, Charles Meneveau;
+ *  A functional form for the energy spectrum parametrizing bottleneck and intermittency effects.
+ *  Physics of Fluids 1 June 2008; 20 (6): 065109.
+ *  https://doi.org/10.1063/1.2936312
  */
 template <field_backend be,
           kspace_dealias_type dt>