Standardize "Ref:" to "Reference" across files (#1210)

Updated all instances of "Ref:" to "Reference" for consistency in both code and documentation. This change improves clarity and aligns with standard terminology practices.

PathTracking/cgmres_nmpc/cgmres_nmpc.py

@@ -4,7 +4,7 @@ Nonlinear MPC simulation with CGMRES
 
 author Atsushi Sakai (@Atsushi_twi)
 
-Ref:
+Reference:
 Shunichi09/nonlinear_control: Implementing the nonlinear model predictive
 control, sliding mode control https://github.com/Shunichi09/PythonLinearNonlinearControl
 

PathTracking/move_to_pose/move_to_pose.py

@@ -76,7 +76,7 @@ class PathFinderController:
         # [-pi, pi] to prevent unstable behavior e.g. difference going
         # from 0 rad to 2*pi rad with slight turn
 
-        # Ref: The velocity v always has a constant sign which depends on the initial value of α.
+        # The velocity v always has a constant sign which depends on the initial value of α.
         rho = np.hypot(x_diff, y_diff)
         v = self.Kp_rho * rho
 

PathTracking/stanley_controller/stanley_controller.py

@@ -4,7 +4,7 @@ Path tracking simulation with Stanley steering control and PID speed control.
 
 author: Atsushi Sakai (@Atsushi_twi)
 
-Ref:
+Reference:
     - [Stanley: The robot that won the DARPA grand challenge](http://isl.ecst.csuchico.edu/DOCS/darpa2005/DARPA%202005%20Stanley.pdf)
     - [Autonomous Automobile Path Tracking](https://www.ri.cmu.edu/pub_files/2009/2/Automatic_Steering_Methods_for_Autonomous_Automobile_Path_Tracking.pdf)