This book discusses the development of new approaches which lead to exact (but not explicit) solutions of key canonical problems like diffraction by an impedance wedge or cone. Includes calculations of the diffraction or excitation coefficients, including their uniform versions, for the diffracted waves from the edge of the wedge or from the vertex of the cone. Study of the farfield behaviour in diffraction by impedance wedges or cones, reflected waves, space waves from the singular points of the boundary (from edges or tips) and surface waves. Applicability of the reported solution...