Apache web server home page: https://www.apache.org/httpd.html
Netcraft web surveys: https://www.netcraft.com/
Apache modules: https://www.apache.org/docs/mod/index.html
The mod_proxy Apache module: https://www.apache.org/docs/mod/mod_proxy.html
The mod_rewrite Apache module: https://www.apache.org/docs/mod/mod_rewrite.html
Author Ralf S. Engelschall's mod_proxy URL Rewriting Guide: https://www.engelschall.com/pw/apache/rewriteguide/
Why are there three config files?: https://www.apache.org/info/three-config-files.html