[README] Show command for external packages provided by OpenCascade

README.md

@@ -107,18 +107,14 @@ Please note that the following requirements need to be installed:
 Frackit requires the [OpenCascade][2] library to be installed on your system.
 You can download the source code [HERE][2],
 and details on the installation can be found [HERE][10].
-Please note that [OpenCascade][2] requires further 3rd party products, of which
-the mandatory ones are Tcl/Tk and FreeType (see this [link][11]).
-Note that on Linux systems, the Tcl/Tk libraries can be installed from the command
-line. For instance, if you use Ubuntu, you can install (version 8.6) by writing
+Please note that [OpenCascade][2] requires further 3rd party products, which are
+listed [HERE][11]. On Debian-based distributions, all of these can be installed
+from the command line via:
 
 ```cpp
-sudo apt-get libtk8.6
-sudo apt-get libtcl8.6
+sudo apt-get install tcllib tklib tcl-dev tk-dev libfreetype-dev libxt-dev libxmu-dev libxi-dev libgl1-mesa-dev libglu1-mesa-dev libfreeimage-dev libtbb-dev libgl2ps-dev
 ```
 
-in a terminal. For more details on how to install them from the sources, see [HERE][11].
-
 ### Building Frackit under Linux
 After [OpenCascade][2] and the other requirements listed above have been installed,
 clone this repository within your folder of choice by typing: