Install gnustep-base-doc by entering the following commands in the terminal:
sudo apt update sudo apt install gnustep-base-doc
Description:
Documentation for the GNUstep Base Library
This package contains the GNUstep Base Library API reference, as well as the GNUstep Base programming manual and GNUstep Coding Standards in Info, HTML and PDF format.
Homepage: http://gnustep.org
Version: 1.25.1-2ubuntu3
Section: universe/doc