Tip for the manual

[Jellevanderwerff]

On Mac OS I got an error saying that the spam package (required by the fields package) could not be installed. That's because I didn't have a fortran compiler installed. Easiest on Mac is to do brew install gcc in a terminal if you have Homebrew installed, and then manually install the spam package. On Linux gcc is installed by default in most distributions, otherwise do sudo apt install gcc.