Reference Letters from your Boss?

If both of them are familiar with your work there is absolutely nothing wrong with asking both of them for references. Otherwise, you have to find someone else. You should get as many people to act as a reference as you can anyway. You never know when one of them may drop out of the picture. Some places ask for two references, some for three, four, and I was even asked to provide five references one time. Boy, you could have really seen me scratching my head trying to come up with five names and then trying to contact them, as I had left the area. Another idea is to get a written letter of reference from someone just in case you lose touch after you have departed a place. This happens quicker than you can blink sometimes. And people usually don't tell you where the missing party has gone. Good luck in finding a new work home.