International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by E. Arnold, D. M. Himmel and M. G. Rossmann © International Union of Crystallography 2012 
International Tables for Crystallography (2012). Vol. F, ch. 19.10, p. 630
Figure 19.10.2.2^{a}National Center for Macromolecular Imaging, 

Figure 19.10.2.2
A representation of the Euler GUI tool. The threedimensional reconstruction is shown (lower left), along with a projection and class average for a particular orientation identified in the asymmetric triangle on the right. Each cylinder in the asymmetric triangle represents a projection direction, with its height representing the number of particles found in that orientation. 