I used the Bien Cuit bread book for the first time and the sourdough rye bread recipe lists two starters, one with sourdough starter and one with a little but of powdered yeast. I am unclear as to whether you are supposed to use one or the other or both! The recipe reads "add the starter" (singular), not the starters (both). I am stymied as to what is the right thing to do. Anyone know?