Bessel functions have the peculiarity of being functions of two independent variables argument and order They have been studied extensively because of their countless applications but the vast majority of available literature is devoted to the case of fixed order variable argument This two volume work explores the opposite case This volume focuses on properties of the functions and mathematical operations with respect to the order Thorough discussion of Bessel and related functions with fixed argument and variable order First book on the topic using this approach Bessel functions find a wide range of applications in mathematics physics chemistry and engineering