Acknowledgements With pleasure.the author thanks Gary Chartrand for the advice and informatior he kindly supplied on many topics described in this book.In addition,the author thanks the and e tions on the first draft of this o her kindnend encouragement in inhi book that an improved book resulted. Acknowledgements With pleasure, the author thanks Gary Chartrand for the advice and information he kindly supplied on many topics described in this book. In addition, the author thanks the reviewer for the valuable input and suggestions on the first draft of this manuscript. Finally, the author is so grateful to Razia Amzad, SpringerBriefs editor, for her kindness and encouragement in writing this book. It is because of all of you that an improved book resulted. vii