Translation at new item and update

Hello,

Sorry to bother, but cannot find the way to override translation of the followings at item submission and update:

"Thank you for your submission!..."
"Item has been saved successfully!"

I have tried to debug language constant and found it, but there is no effect to it - ITEM_SAVED_SUCCESSFULLY

Can you please help?

Thank you again, this is my last request for help :)
Kind regards
Attila