In a non-stick skillet over a medium heat, melt butter and mix with olive oil. Meanwhile coat chicken breasts with flour. Place chicken breasts in skillet and brown both sides. Add lemon juice to broth. When chicken is brown on both sides, pour broth with lemon juice into the skillet, cover tightly with a lid, and turn heat down to medium low. Simmer for 15 minutes. Remove cover from skillet and reduce broth until thicked. Remove chicken breasts and pour thickened sauce over top.