If a sitter has reviews from registered Mindahome home owners, they are genuine and will appear on their profile page on the right under their photos if using a PC, laptop or tablet. If using a phone they are beneath the "Contact sitter" area on their profile page. You can see their profile by clicking their profile title at the top of your conversation with them on your Messages page.
References from other sources may appear as downloadable links beneath their profile description or they will attach them to messages they send you. Some sitters add the names and phone numbers of referees to their application. If they don't do any of these, you will have to ask them to provide you with their references, including the phone numbers of the people that wrote them, so that you can ring and talk to them.