List of fixed groups

[MilesChap]

In the Samsung Galaxy Note GT-N7000 Google has placed several groups which should not be removed (else risk capability to sync with Thunderbird). I have added several groups and need to know which ones can be deleted or not deleted. For instance there are Co-Workers with 1 contact I added, and there are 2 Coworkers with zero contacts. Which 2 of these can be deleted?

 

[MilesChap]

Hasn't been a reply in a couple of days. If my question is unclear please let me know. (FYI, I believe the fixed groups are family, friends, co-workers, and perhaps others -- are these 3 correct? Also I read somewhere that if one of these is deleted that the way to correct it is to add it to google voice. Does anyone know how to go about that?
Miles