OS X - El Capitan - How To Remove unused services from "Services" context menu

I'm would like to remove entries from the Keyboard Services list (Sys Prefs > Keyboard > Shortcuts > services) because they are either obsolete or unused. Indeed some entries are zombie entries because the referred application was uninstalled.

See attached screenshots example1 and example2

Here Mailplane 3 and Prizmo Apps were removed months ago ..

What I would like is also a command line approach to the solution in order to understand how the App are registering the services.. but of course a more visual approach (GUI) is also welcome ;-) Thanks for your valuable help