Add reference sources and update comments

src/jaxsim/rbda/contacts/relaxed_rigid.py

@@ -21,62 +21,62 @@
 class RelaxedRigidContactsParams(ContactsParams):
     """Parameters of the relaxed rigid contacts model."""
 
-    # Time constant
+    # Time constant.
     time_constant: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.01, dtype=float)
     )
 
-    # Adimensional damping coefficient
+    # Adimensional damping coefficient.
     damping_coefficient: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(1.0, dtype=float)
     )
 
-    # Minimum impedance
+    # Minimum impedance.
     d_min: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.9, dtype=float)
     )
 
-    # Maximum impedance
+    # Maximum impedance.
     d_max: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.95, dtype=float)
     )
 
-    # Width
+    # Width.
     width: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.0001, dtype=float)
     )
 
-    # Midpoint
+    # Midpoint.
     midpoint: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.1, dtype=float)
     )
 
-    # Power exponent
+    # Power exponent.
     power: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(1.0, dtype=float)
     )
 
-    # Stiffness
+    # Stiffness.
     stiffness: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.0, dtype=float)
     )
 
-    # Damping
+    # Damping.
     damping: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.0, dtype=float)
     )
 
-    # Friction coefficient
+    # Friction coefficient.
     mu: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(0.5, dtype=float)
     )
 
-    # Maximum number of iterations
+    # Maximum number of iterations.
     max_iterations: jtp.Int = dataclasses.field(
         default_factory=lambda: jnp.array(50, dtype=int)
     )
 
-    # Solver Tolerance
+    # Solver tolerance.
     tolerance: jtp.Float = dataclasses.field(
         default_factory=lambda: jnp.array(1e-6, dtype=float)
     )
@@ -172,7 +172,15 @@ def valid(self, model: js.model.JaxSimModel) -> bool:
 
 @jax_dataclasses.pytree_dataclass
 class RelaxedRigidContacts(ContactModel):
-    """Rigid contacts model."""
+    """
+    Relaxed rigid contacts model.
+
+    Notes:
+        This model is based on the following paper:
+            https://ieeexplore.ieee.org/document/5979814
+        and the code is based on the following implementation:
+            https://github.com/google/brax/blob/main/brax/generalized/constraint.py
+    """
 
     parameters: RelaxedRigidContactsParams = dataclasses.field(
         default_factory=RelaxedRigidContactsParams