International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 9.2, p. 752

Figure 9.2.1.2 

D. Pandeyc and P. Krishnab
[Figure 9.2.1.2]
Figure 9.2.1.2

(a) Symmetry axes of a single close-packed layer of spheres and (b) the minimum symmetry of a three-dimensional close packing of spheres.