diff --git a/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairSpringSliderDashpot/PairSpringSliderDashpot.H b/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairSpringSliderDashpot/PairSpringSliderDashpot.H
index a0bddd2682..192973f99d 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairSpringSliderDashpot/PairSpringSliderDashpot.H
+++ b/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/PairModel/PairSpringSliderDashpot/PairSpringSliderDashpot.H
@@ -27,6 +27,15 @@ Class
 Description
     Pair forces between particles colliding with a spring, slider, damper model
 
+    Reference:
+    \verbatim
+        "Lagrangian numerical simulation of plug flow of cohesionless
+         particles in a horizontal pipe"
+        Tsuji, Y., Tanaka, T., Ishida, T.,
+        Powder Technology
+        Volume 73, Issue 3, September 1992, pp. 239-250
+    \endverbatim
+
 \*---------------------------------------------------------------------------*/
 
 #ifndef PairSpringSliderDashpot_H
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallLocalSpringSliderDashpot/WallLocalSpringSliderDashpot.H b/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallLocalSpringSliderDashpot/WallLocalSpringSliderDashpot.H
index 712825580e..5cdbea4ec4 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallLocalSpringSliderDashpot/WallLocalSpringSliderDashpot.H
+++ b/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallLocalSpringSliderDashpot/WallLocalSpringSliderDashpot.H
@@ -28,6 +28,15 @@ Description
     Forces between particles and walls, interacting with a spring,
     slider, damper model
 
+    Reference:
+    \verbatim
+        "Lagrangian numerical simulation of plug flow of cohesionless
+         particles in a horizontal pipe"
+        Tsuji, Y., Tanaka, T., Ishida, T.,
+        Powder Technology
+        Volume 73, Issue 3, September 1992, pp. 239-250
+    \endverbatim
+
 \*---------------------------------------------------------------------------*/
 
 #ifndef WallLocalSpringSliderDashpot_H
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallSpringSliderDashpot/WallSpringSliderDashpot.H b/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallSpringSliderDashpot/WallSpringSliderDashpot.H
index e76b064e0a..210299b943 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallSpringSliderDashpot/WallSpringSliderDashpot.H
+++ b/src/lagrangian/intermediate/submodels/Kinematic/CollisionModel/PairCollision/WallModel/WallSpringSliderDashpot/WallSpringSliderDashpot.H
@@ -28,6 +28,15 @@ Description
     Forces between particles and walls, interacting with a spring,
     slider, damper model
 
+    Reference:
+    \verbatim
+        "Lagrangian numerical simulation of plug flow of cohesionless
+         particles in a horizontal pipe"
+        Tsuji, Y., Tanaka, T., Ishida, T.,
+        Powder Technology
+        Volume 73, Issue 3, September 1992, pp. 239-250
+    \endverbatim
+
 \*---------------------------------------------------------------------------*/
 
 #ifndef WallSpringSliderDashpot_H