Of the topics discussed in this book special mention may perhaps be made of the representation of Theory of Linear Associative Algebras. With a fuIl analysis of the ideal resolution and the determination of the irreducible representations of the Dirac and Kemmer algebras, the repre- sentations of the symmetrie group via Young tableaux with application to the construction of the symmetry classes of tensors useful in the study of assemblies of identical particles, a systematic derivation of the 32 crys- taIlographic point-groups, and exhaustive discussion of the structure and representations of the Lorentz group and abrief introduction to Dynkin diagrams in the classification of Lie groups. Wigner's derivation of the Clebsch-Gordan coefficients, with a minor simplification has also been included in an Appendix to Chapter 8 on the Rotation group and its representations.