Under the graph you'll find 5 people (1 gray picture + 4 faces) who are either Anonymous (grey face), your contacts or people you can connect on Linkedin. Do it! I do it.
Write them personalized email.
If you don't have a premium package (paid Linkedin account) you can only see 5 people. I have only 5 people shown by the Linkedin, I use Linkedin for free, to be able to tell you how to really use Linkedin.