Test latex in readme

README.md

@@ -42,7 +42,8 @@ for additional info regarding user defined types and (constructors)[https://docs
 The interface `AbstractProcess` defines the functions `control(P, u)` and `measure(P)`.
 These functions can be used to implement your own control loops. A common loop
 with a feedback controller and a feedforward filter on the reference is implemented
-in the function [`run_control_2DOF`](@ref).
+in the function [`run_control_2DOF`](@ref), where the user can supply $G_1$ and $G_4$
+in the diagram below, with the process $P=G_2$.
 ![block diagram](docs/feedback4.png)
 
 The macro `@periodically` might come in handy if you want to implement your own loop.