You can find this exercise on page 31 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: FLEXIBILITY, HIPS, LEGS - FEET
Begin on your hands and knees. Take your left knee forward resting the entire outside of the leg on the ground. Keep your knee and thigh facing forward as your foot crossing over the center line toward your right hip. Try to keep your hips level. To intensify the stretch, lift through and bend forward.