2001 Quaternionic Structures in Mathematics and Physics  
These notes are based on a I talk I gave at the Erwin Schr dinger International Institute for Mathematical Physics, Vienna, on the 20th October, 1999. This is work in progress, partly based on joint work with F. M. Cabrera and M. D. Monar and partly results of my Ph. D. student Richard Cleyton. It is a pleasure to thank the Erwin Schr dinger Institute and the organisers of the program on Holonomy Groups in Di erential Geometry for their kind hospitality.
doi:10.1142/9789812810038_0026 fatcat:lvyqm2nwcvfp5llu3za65us3fy