"Based on lectures given at a conference on integrable systems organized by N.M.J. Woodhouse and held at the Mathematical Institute, University of Oxford, in September 1997".
Integrable systems : twistors, loop groups, and Riemann surfaces by N. J. Hitchin. ISBN 0198504217. Published by Clarendon Press in 1999. Publication and catalogue information, links to buy online and reader comments.