slight changes

README.md

@@ -83,10 +83,11 @@ where it improves legibility. Consult the source files for more information.
 A drum is described by a set of (static) parameters (stiffness, mass, x-y position, etc),
 which are to be stored in a container of type `params_t`. The variables (displacement, velocity,
 electrode charges, etc.) are stored in a container of type `vars_t`. Example classes for
-these two types are included in the lib folder. However, these containers likely need to
-be adapted to the situation at hand. When time evolving, the stepper will use the container of
+these two types are `lib/drum_parameters.hpp` and `lib/drum_variables.hpp`.
+However, these containers likely need to be adapted to the situation at hand.
+When time evolving, the stepper will use the container of
 type `sbuffer_t` to store its intermediate results. Note that the default constructor of
-this class is `delete`d. It should be constructed from an object of type `params_t`.
+this class is `delete`'d. It should be constructed from an object of type `params_t`.
 
 ### Interface template type `Force` (`force.hpp`), force functional
 1. Template arguments