New material in the second online edition of Volume B

Chapter 1.5 on classifications of space-group representations in reciprocal space has been extensively revised.

Chapter 2.2 on direct methods has been extended to include applications of these methods to macromolecular crystallography.

Chapter 2.3 on Patterson and molecular replacement techniques has been updated and extended.

Chapter 2.5 on electron diffraction and microscopy has been updated. Section 2.5.3 on convergent-beam electron diffraction has been completely rewritten by M. Tanaka. Section 2.5.6 on three-dimensional reconstruction has been updated and extended by P. Penczek, who has also written a new Section 2.5.7 on single-particle reconstruction. The Foreword to the chapter has also been revised by J. C. H. Spence.

Chapter 3.3 on molecular graphics has been extended by a new section on the implementation of molecular graphics to small and medium-sized molecules by L. M. D. Cranswick.

Chapter 3.5 on modern extensions of Ewald methods by T. A. Darden is new and deals with the inclusion of fast Fourier transforms in the computation of sums and the departure from the point-charge model in Ewald summations.

Chapter 4.1 on thermal diffuse scattering of X-rays and neutrons has been updated.

Chapter 4.2 on disorder diffuse scattering of X-rays and neutrons has been extensively revised and updated.

Minor revisions and corrections have also been made to Chapters 1.1, 1.2, 1.4, 2.1, 4.4, 4.6 and 5.1.