Twistors in mathematics and physics

1. Twistor theory after 25 years - its physical status and prospects R. Penrose 2. Between integral geometry and twistors S. G. Gindikin 3. Generalized conformal structures S. G. Gindikin 4. Riemannian twistor spaces and holonomy groups F. E. Burstall 5. Twistors, ambitwistors, and conformal gravity C. R. LeBrun 6. The Penrose transform M. G. Eastwood 7. Notation for the Penrose transform E. G. Dunne 8. The twistor transform E. G. Dunne and M. G. Eastwood 9. Invariant operators R. J. Baston and M. G. Eastwood 10. Penrose's quasi-local mass K. P. Tod 11. The sparkling 3-form, Ashtekar variables and quasi-local mass L. J. Mason and J. Frauendiener 12. Twistor and strings W. T. Shaw and L. P. Hughston 13. Integrable systems in twistor theory R. S. Ward 14. Twistor characterization of stationary axisymmetric solutions of Einstein's equations J. Fletcher and N. M. J. Woodhouse 15. A two-surface encoding of radiative space-times C. N. Kozameh, C. J. Cutler and E. T. Newman 16. Twistors, massless fields and the Penrose transform T.N. Bailey and M. A. Singer 17. Twistor diagrams and Feynman diagrams A. P. Hodges 18. Cohomology and twistor diagrams S. A. Huggett Authors' addresses.