I would like to thank the following people who have helped in one way or another with this book:

Jack Ainsworth, Norma Clark, Ben Edwards, Ann Lightbown, Alan Mills, Andy Stewart, Alan Stott, and Gerry Wolstenholme. I am also indebted to the late Alan McLerie and the late Frank Singleton for information readily supplied. As much of my research was undertaken for a talk given some years ago, there may be others whom I have overlooked, for which I apologise.

T. L.