I would like to acknowledge the encouragement given by my wife, Irma, and my daughters, Corinne and Kathryn, whose mother, Eunice, was herself a dedicated teacher and a major inspiration for the book.

I am grateful for the assistance given in the typing of the book by Nerle Nelson, Magaly Vázquez and Patricia Brady and in the editing by Jean Vasconcellos.

Space does not permit me to mention the names of so many other people who have provided constant motivation and intellectual stimulation throughout the writing of the book.