g 2/14 p. 7

w02 7/15 p. 29

w00 6/15 pp. 3-4

w00 6/15 pp. 6-7

w00 8/1 pp. 29-31

ijwyp article 68

yp2 chap. 27

yp2 p. 227

g03 7/22 pp. 11-13

g03 8/22 pp. 17-19