Finch, S. R. Mathematical Constants. Cambridge, England: Cambridge University Press, 2003.Goudsmit,
S. "Random Distribution of Lines in a Plane." Rev. Mod. Phys.17,
231-322, 1945.Santaló, L. A. "Sobre la distrabucion
de planos en el espacio." Rev. Unión Mat. Argentina13,
120-124, 1948.Santaló, L. A. Integral
Geometry and Geometric Probability. Reading, MA: Addison-Wesley, 1976.Sloane,
N. J. A. Sequence A000124/M1041
in "The On-Line Encyclopedia of Integer Sequences."Trott,
M. "Coloring Closed Curves." §1.6 in The
Mathematica GuideBook for Graphics. New York: Springer-Verlag, pp. 393-430,
2004. http://www.mathematicaguidebooks.org/.
into which 
lines divide a square is
,
2, ..., this gives 2, 4, 7, 11, 16, 22, ... (OEIS A000124),
which is the same number into which the plane, a circle, etc. can be divided.
