Th. Hahn demonstrated two new features of the Fourth Edition (1996) of Volume A, Space-Group Symmetry: completion of the space-group diagram project for all 17 plane and 230 space groups, and introduction of the double glide plane e by means of new graphical symbols for 17 space-group diagrams and modifications of five orthorhombic space-group symbols.

The plans for the Second Edition of Volume B, Reciprocal Space, were presented by the editor U. Shmueli. In addition to corrections and major revisions of several existing chapters the Second Edition will contain five new contributions on the following topics:

• Space-group representations in reciprocal space.
• Direct methods in electron crystallography.
• Diffraction by polymers.
• Reciprocal-space images of aperiodic crystals.
• Dynamical theory of neutron diffraction.

The editor of Volume C, Mathematical, Physical and Chemical Tables, E. Prince, explained that the preparations for the Second Edition of this Volume (scheduled for publication in 1997) were about 85% complete at the time of death of the previous editor, A.J.C. Wilson. The rest is presently being edited. Due to rapid obsolence of much of the tabular material in this volume, an electronic version of Vol. C is presently under active consideration.

The new Volume D, Physical Properties of Crystals, scheduled for 1998, was introduced by its editor A. Authier. It consists of three parts:

• Part 1 treats Tensorial Aspects of Physical Properties; it contains both the general mathematical background and the individual physical properties.
• Part 2 is devoted to the Symmetry Aspects of Excitations (phonons, electrons, Raman scattering, Brillouin scattering).
• Part 3 is devoted to the Symmetry Aspects of Structural Phase Transitions, Twinning and Domain Structures.

The new Volume E, Subperiodic Groups, is edited by V. Kopsky and D.B. Litvin. Its publication is planned for 1998. The volume is devoted mainly to Layer and Rod Groups, i.e. to groups in three dimensions with lattices of only two or one dimensions.

The volume consists of two parts:

• Part 1: Subperiodic group tables: Frieze, Rod and Layer Groups.
• Part 2: Scanning of space groups, i.e. layer groups as subgroups of space groups.

Volume A1, Maximal Subgroups of Space and Plane Groups, was introduced by its editor H. Wondratschek. It is a companion volume to Vol. A and completes the treatment of the maximal subgroups of space groups. Complete lists of maximal subgroups of indices 2, 3, and 4 will be given. The infinitely many maximal isomorphic subgroups will be presented by formulae with the index as parameter. Classes of conjugate subgroups will be indicated.

The final project of the session was presented by T. Janssen: Volume A2, N-Dimensional Crystallography. This volume consists of a computer programme (CD-ROM) and an accompanying printed volume with a manual and a treatment of the theory of symmetry in arbitrary dimension. This implies that it gives the information on two- and three-dimensional point groups as well. For more than three dimensions these groups are used already by crystallographers dealing with incommensurate phases and quasicrystals. From a data base are calculated the space groups, the symmetry elements, the Wyckoff positions, the general and special extinction rules, in short all that can be found in the existing tables for 2 and 3 dimensions.