International
Tables for Crystallography Volume C Mathematical, physical and chemical tables Edited by E. Prince © International Union of Crystallography 2006 
International Tables for Crystallography (2006). Vol. C, ch. 9.2, p. 755


Figure 9.2.1.7
A rhombohedral lattice (a_{1}, a_{2}, a_{3}) referred to hexagonal axes (A_{1}, A_{2}, C)(after Buerger, 1953). 