You can find this exercise on page 124 of the book Synergistic Golf.
Exercise Type: DYNAMIC STRETCH
Exercise Category: ABDOMINALS, FLEXIBILITY, SHOULDERS
Stand tall with feet a little wider than hip distance apart. Clasp arms over head reaching tall. Slowly bend to the right without shifting weight in hips or feet first. Then slowly shift weight in hips and feet to the left slightly for maximum stretch. Continue pulling arms away from body. Repeat each side 5x.