In the introduction to his book Dr. Harder has very clearly described its purpose and organization. I only want to add for the English-speaking reader a few words on the place the present text is likely to have in the cur­ rent literature. At first Dr. Harder's undertaking might come as a surprise. Only a few years ago, Zeisel's Say it with Figures gave the market research practi­ tioner some ideas of how simple figures and tables could be successfully employed; Langhoff's publication for the American Marketing Associa­ tion presented some pertinent mathematical models in the most elemen­ tary form; why should a German author believe he can already introduce us to serious mathematical procedures for use in product management and advertising? After reading the book, incredulity turns into pleasure because of the skill with which the author has pursued his task. As a matter of fact, the book can serve two audiences who at first glance might appear to have quite opposing interests. For the mathematically trained market re­ searcher, the book has the marked advantage of combining a variety of ap­ proaches not ordinarily mixed in one volume. If the market researcher be­ gan as an economist he is already familiar with difference equations and time series analysis; if he moved in from psychology, he is already ac­ quainted with factor analysis. But as he reads this book, he finds the two worlds well integrated.