CLEVELAND, WILLIAM S. The Elements of Graphing Data, rev. ed., Hobart Press, Summit, N.J., 1994. A careful study of the most effective elementary ways to present data graphically, with much sound advice on improving graphs such as scatterplots.

LESSER, LAWRENCE M. The “Ys” and “why nots” of line of best fit, Teaching Statistics, 21(2) (1999): 54–55.

MOORE, DAVID S., WILLIAM I. NOTZ, and MICHAEL A. FLIGNER. The Basic Practice of Statistics (BPS), 7th ed., Freeman, New York, 2015. Chapters 4 and 5 of BPS give more extensive treatment of FAPP Chapter 6 material, at about the same mathematical level.