* free_use_share (by-nc-nd)
* free_use_share_commercially (by-nd)
* free_use_share_modify (by-nc-sa)
* free_use_share_modify_commercially (by-sa)
These labels can be used to restrict all custom search content to Creative Commons results or to help refine searches. The CC labels are filter labels.
Google also took the opportunity to remind us of how to document Creative Commons license. They gave four examples of the many ways licenses can be documented on an HTML file:
Google Adds Option to Limit to Creative Commons Licensed Material