"This monograph develops a mathematical theory of gravitational lensing. The theory applies to any finite number of deflector planes and highlights the distinctions between single and multiple plane lensing.". "Examples, illustrations, bibliography and index make this a suitable text for an undergraduate/graduate course, seminar, or independent thesis project on gravitational lensing. The book is also a reference text for professional mathematicians, mathematical physicists, astrophysicists, and physicists."--BOOK JACKET.