Part of the World University Library. "The WOrld University Library os an international series of books, each of which has been specially commissioned. The authors are leading scientists and scholars from all over the world who, in an age of increasing specialization, see the need for a broad, up-to-date presentation of their subject. The aim is to provide an authoritative introductory books for university students which will be of interest also to the general reader. the series is published in Britain, France, Germany, Holland, Italy, Spain, Sweden and the Unites States."