Hi. Our oldest daughter is 3yrs 2mo old. Our youngest daughter is 11mo. Within the past month or so, our oldest daughter has started hitting and pushing our youngest daughter. Oftentimes this leads to our baby falling backwards and hitting her head on the hardwood floors. Obviously this is a major concern to us for the safety of the baby. This happens either provoked (e.g. baby has a toy the 3-year old wants) or unprovoked (3-year old comes from across the room and pushes the baby). What is the best method of discipline for the 3-year old? What can we do to prevent this? What can we do to further protect the baby from this kind of harm?