' … applies all tools of classical and quantum measurement to the measurement of small forces. The tools include evolution operators, eigenstates, density matrices, correlation functions, noise spectral densities and hetero- and homodyne detection … the ideas, all subtle, fundamental and useful, are the original work of the authors … will provide easy-to-understand examples for the quantum mechanics texts of the future, and it will influence the direction of research in quantum mechanics.' Donald Searl, Physics Today