In order to remove those links from your Reader you can follow steps as given below.
1) Open Digital Editions on your computer.
2) Connect your Reader to your computer.
3) Now the Reader will show up in Bottom left side of Digital Editions screen in form of an icon.
4) Clisk on Reader Icon and it will show up all the contents on your Reader.
5) Drag the cursor on the book which you want to delete.
6) Once you will drag icon on the book a very small arrow kind of option will show up on the top right corner of Book.
7) Click on the arrow and it will give you an option to Delete item.
8) Click on Delete Item and it will be removed from your Nook Reader.
I hope this will help you.
Thanks for the response. I will try that.