Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: A must have book for scientists and engineers

As an undergraduate physics major who didn't want to take a differential equations class, this book is a real life saver. The book gives the reader a working knowledge of fourier series and orthogonal functions (Bessel, legendre, laguerre, etc) while also providing enough mathematical rigor for the reader to understand the motivation and nature of the functions themselves. Personally, this book came in handy when trying to understand quantum mechanics where the equations can get very algebraically thorny. It's a cheap book and worth a whole lot more than it costs.