How do I completely remove (not just switch off) entries from Notification Center

In the notification center (inside system settings) I am full of websites that have permission to end notifications. I have been able one by one to turn off permission but I also would like to delete them completely from there. The best I can do seems to be to HIDE them.. but not REMOVE THEM ! I checked inside Safari and removed all the ones in there but there are still many others that are in the Notification Center AND NOT in Safari. How do I just REMOVE THEM completely?