1. Andre Barre, Albert Flocon, and Robert Hansen, Curvilinear Perspective, Berkeley and Los Angeles, Univ. of California Press, 1987.
2. F.H. Bool, Bruno Ernst, J.R. Kist, J.L. Locher, F. Wierda. M.C. Eschen His Lifeand Complete Graphic Work, London: Thames and Hudson; New York, Harry N. Abrams, 1982.
3. A.R. Branum and K.C. Thornton, “Illusion of Rotary Motion Reversal in a Sphere Is Facilitated by Increased Rotational Speed,” Perceptual and Motor Skills 73 (1991) 627–634.
4. Fernando R. Casas, “Flat Sphere Perspective,” Leonardo 16, No. 1 (1988) 1–9
5. Fernando R. Casas, “Polar Perspective,” Leonardo 17, No. 3 (1984) 188–194.