ACKNOWLEDGEMENTS:

I wish to acknowledge and thank those who have assisted me in the research and preparation of this thesis. First I would like to thank my supervisor, Dr Elizabeth J. Billington, who has on countless occasions given me invaluable guidance and advice. Thanks also to Dr Diane Donovan, Dr Sheila Williams and Dr Ebad S. Mahmoodian for their assistance and encouragement during this work.

Secondly, I would like to thank the Department of Mathematics at the University of Queensland and in particular the Head of the Department, Dr Vincent Hart, for providing the Departmental scholarship and tutorial positions to support me financially. I also thank Dr Martin Sharry and Peter Adams for providing computing expertise.

Finally, I thank my family, particularly my wife, Sarah, who has taken on many extra responsibilities.