- Read more about file descriptors at the following link: https://linuxmeerkat.wordpress.com/2011/12/02/file-descriptors-explained/.
- Find information about advanced scripts with file descriptors at the following link: https://bash.cyberciti.biz/guide/Reads_from_the_file_descriptor_(fd).
- Read more about command substitution at the following link: http://www.tldp.org/LDP/abs/html/commandsub.html.
- Find information about here documents at the following link: https://www.tldp.org/LDP/abs/html/here-docs.html.