[TYPO3-calendar] calendar base backend edit mask only visible to admin users

[Martin]

I'm using calendar  base.

If I'm logged in as Admin, all is working fine. When logging in as non 
admin and opening an exiting or a new entry, the edit mask is not shown 
at all. I've given list end edit permissions on tables

Calendar Category, Calendar Event, Calendar Exception Event, Calendar 
Exception Event Group, Calendar Event Location,  Calendar Event 
Organizer and Event Attendee

I can't find any additional needed rights for backend editing in the 
documentation. What am I missing here?

Cheers

Martin Wroblinski