Add ref to better FFD-tutorial where needed

Author: TobiKattmann

_tutorials/design_features/Inviscid_3D_Constrained_ONERAM6/Inviscid_3D_Constrained_ONERAM6.md

@@ -101,7 +101,7 @@ FFD_CONTINUITY= 2ND_DERIVATIVE
 
 As the current implementation requires each FFD box to be a quadrilaterally-faced hexahedron (6 faces, 12 edges, 8 vertices), we can simply specify the 8 corner points of the box and the polynomial degree we would like to represent along each coordinate direction (x,y,z) in order to create the complete lattice of control points. It is convenient to think of the FFD box as a small structured mesh block with (i,j,k) indices for the control points, and note that the number of control points in each direction is the specified polynomial degree plus one. 
 
-In the example above, we are creating a box with control point dimensions 11, 9, and 2 in the x-, y-, and z-directions, respectively, for a total of 198 available control points. In the `FFD_DEFINITION` option, we give a name to the box ("WING"), and then list out the x, y, and z coordinates of each corner point. The order is important, and you can use the example above to match the convention. The degree is then specified in the `FFD_DEGREE` option. A view of the box with the control points numbered is in Figure (3). Note that the numbering in the figure is 1-based just for visualization, but within SU2, the control points have 0-based indexing. For example, the (1,1,1) control point in the figure is control point (0,0,0) within SU2. This is critical for specifying the design variables in the config file.
+In the example above, we are creating a box with control point dimensions 11, 9, and 2 in the x-, y-, and z-directions, respectively, for a total of 198 available control points. In the `FFD_DEFINITION` option, we give a name to the box ("WING"), and then list out the x, y, and z coordinates of each corner point. The order is important, and you can use the example above to match the convention. Alternatively, [this tutorial](/tutorials/Species_Transport/) contains more in-depth information on how the numbering should be done. The degree is then specified in the `FFD_DEGREE` option. A view of the box with the control points numbered is in Figure (3). Note that the numbering in the figure is 1-based just for visualization, but within SU2, the control points have 0-based indexing. For example, the (1,1,1) control point in the figure is control point (0,0,0) within SU2. This is critical for specifying the design variables in the config file.
 
 ![Opt. ONERA FFD](../../tutorials_files/design_features/Inviscid_3D_Constrained_ONERAM6/images/onera_ffd_points.png)
 Figure (3): View of the control point identifying indices, which increase in value along the positive coordinate directions. Note that the numbering here is 1-based just for visualization, but within SU2, the control points have 0-based indexing.

_tutorials/design_features/Multi_Objective_Shape_Design/Multi_Objective_Shape_Design.md

@@ -71,7 +71,7 @@ OBJECTIVE_WEIGHT= -1.0E-7,1.0
 ```
 These options define a weighted sum: -1.0E-7 x (SURFACE_TOTAL_PRESSURE at the outlet) + (DRAG on the lower surface). The OBJECTIVE_FUNCTION and OBJECTIVE_WEIGHT options are set automatically during the optimization process, and are used for the calculation of the gradient. If we were starting this problem from scratch, at this point we would run the gradient method desired, in order to confirm that the gradients are being calculated as expected. In this tutorial, the discrete adjoint is used by default. When multiple objectives are specified as shown, a single adjoint solution for a 'combo' objective will be calculated, representing the gradient for the weighted sum. The upside of this is that it reduces the number of adjoint solutions required, with the downside that the contributions of different functionals to the gradient value will not be known.
 
-Next the FFD box is defined in order to provide the design variables. The mesh is provided with the FFD box information already included, however when starting from scratch a preprocessing step using SU2_MSH is required. For further detail on FFD, see the [Constrainted Optimal Shape Design Tutorial](/tutorials/Inviscid_3D_Constrained_ONERAM6/).
+Next the FFD box is defined in order to provide the design variables. The mesh is provided with the FFD box information already included, however when starting from scratch a preprocessing step using SU2_MSH is required. For further detail on FFD, see this [Unconstrained species transport tutorial](/tutorials/Species_Transport/) or [Constrainted Optimal Shape Design Tutorial](/tutorials/Inviscid_3D_Constrained_ONERAM6/).
 ```
 % -------------------- FREE-FORM DEFORMATION PARAMETERS -----------------------%
 %

_tutorials/design_features/Species_Transport/Species_Transport.md

@@ -14,7 +14,7 @@ follows: Inc_Species_Transport
 
 ## Disclaimer
 
-This Tutorial builds directly on the case given as Prerequisite on the top of the site [link](tutorials/Inc_Species_Transport/). Therefore details to the problem setup, mesh, etc. are not repeated here. However the process outlined in this tutorial is directly applicable to many other cases using SU2.
+This Tutorial builds directly on the case given as Prerequisite on the top of the site [link](/tutorials/Inc_Species_Transport/). Therefore details to the problem setup, mesh, etc. are not repeated here. However the process outlined in this tutorial is directly applicable to many other cases using SU2.
 
 Instead of the python tools for finite differences or shape optimization that are part of SU2 directly, the standalone python tool [FADO](https://github.com/su2code/FADO) is used. Please follow the information on the given github repo in order to use FADO.
 

_tutorials/design_features/Unsteady_Shape_Opt_NACA0012/Unsteady_Shape_Opt_NACA0012.md

@@ -42,6 +42,8 @@ in the [project website repository](https://github.com/su2code/Tutorials).
 You will need the configuration file ([unsteady_naca0012_opt.cfg](https://github.com/su2code/Tutorials/tree/master/design/Unsteady_Shape_Opt_NACA0012/unsteady_naca0012_opt.cfg)) and 
 the mesh file ([unsteady_naca0012_FFD.su2](https://github.com/su2code/Tutorials/tree/master/design/Unsteady_Shape_Opt_NACA0012/unsteady_naca0012_FFD.su2)).
 
+The used mesh already contains an FFD-Box. For more information on how to set up an FFD-Box on your own, please follow [this tutorial](/tutorials/Species_Transport/).
+
 ## Tutorial ##
 
 The following tutorial will walk you through the steps required when performing a shape optimization of the  NACA0012 airfoil using SU2. 
@@ -51,7 +53,7 @@ If you have yet to complete these requirements, please see the [Download](/docs_
 
 ### Background ###
 
-This test case is for the NACA0012 airfoil in viscous unsteady flow. The NACA airfoils are two dimensional shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA, 1915-1958, predeccessor of NASA). The NACA-4-Digit series is a set of 78 airfoil configurations which were created for wind-tunnel tests to explore the effect of different airfoil shapes on aerdynamic coefficients as drag or lift. 
+This test case is for the NACA0012 airfoil in viscous unsteady flow. The NACA airfoils are two dimensional shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA, 1915-1958, predecessor of NASA). The NACA-4-Digit series is a set of 78 airfoil configurations which were created for wind-tunnel tests to explore the effect of different airfoil shapes on aerodynamic coefficients as drag or lift.
 
 ### Mesh Description ###