Hello Bob,
That screenshot is for an old reference system. I joined as a host in October 2016 and haven't seen that "Request references" tab.
Bob, Gynne and Meltem,
I'm not sure if ye've done this already but you have to connect your Airbnb and Facebook accounts for the references feature to work.
Currently the only way to get references is through Facebook. You must connect your Airbnb account with your Facebook account and your friends must also have an Airbnb account.
If that's done, then as Wendy says, your Facebook friends who are already registered with Airbnb will appear on the references page.
If ye have already connected the accounts and your Facebook friends have an Airbnb account but it still doesn't work then contact Airbnb support.
Steve.