1 Notation, 2 Elementary Properties, 3 Polynomials, 4 Linear Difference Equations, 5 Classification of Sums, 6 Gosper’s Algorithm, 7 Sums of Type II(1,1,z), 8 Sums of Type II(2,2,z), 9 Sums of Type II(3,3,z), 10 Sums of Type II(4,4,±1), 11 Sums of Type II(5,5,1), 12 Other Type II Sums, 13 Zeilberger’s Algorithm, 14 Sums of Types III–IV, 15 Sums of Type V, Harmonic Sums, A Indefinite Sums, B Basic Identities