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

International Tables for Crystallography (2006). Vol. C. ch. 4.2, p. 195

Figure 4.2.1.4 

U. W. Arndta
[Figure 4.2.1.4]
Figure 4.2.1.4

The function μ in Müller's equation (equation 4.2.1.12[link]) as a function of the ratio of width to length of the focal spot.