After importing references from various sources, you may have duplicate references in your Library. Mendeley has a simple function to weed out these duplicates for you.
Go to Tools > Check for Duplicates
Mendeley has Groups that you can join to network or share your research with.
You can join any of the public groups available or create your own with your own research group.
To find out more on Groups, visit Mendeley's guide: https://www.mendeley.com/guides/groups