https://addons.opera.com/nl/extensions/details/mp3cow/
Extensie MP3Cow - Opera-add-ons
Convert YouTube Videos to mp3 files with MP3Cow
extensieoperaaddons
https://addons.opera.com/fr/extensions/details/mp3cow/
Extension MP3Cow - Add-ons Opera
Convert YouTube Videos to mp3 files with MP3Cow
add onsextensionopera