参考文献

Homepage: https://www.virtualbox.org/
Online User Manual: https://www.virtualbox.org/manual/UserManual.html
End-user documentation: https://www.virtualbox.org/wiki/End-user_documentation
Technical documentation: https://www.virtualbox.org/wiki/Technical_documentation
Timeline: https://www.virtualbox.org/timeline?daysback=10
Changelog: https://www.virtualbox.org/wiki/Changelog
/opt/VirtualBox/UserManual.pdf：安装目录下的PDF文档