1. Relativistic Wave Equation for Spin-0 Particles The Klein-Gordon Equation and Its Applications.- 1.1 The Notation.- 1.2 The Klein-Gordon Equation.- 1.3 The Nonrelativistic Limit.- 1.4 Free Spin-0 Particles.- 1.5 Energy-Momentum Tensor of the Klein-Gordon Field.- 1.6 The Klein-Gordon Equation in Schrödinger Form.- 1.7 Charge Conjugation.- 1.8 Free Spin-0 Particles in the Feshbach-Villars Representation.- 1.9 The Interaction of a Spin-0 Particle with an Electromagnetic Field.- 1.10 Gauge In variance of the Coupling.- 1.11 The Nonrelativistic Limit With Fields.- 1.12 Interpretation of One-Particle Operators in Relativistic Quantum Mechanics.- Biographical Notes.- 2. A Wave Equation for Spin-$$\frac{1}{2}$$ Particles - The Dirac Equation.- 2.1 Free Motion of a Dirac Particle.- 2.2 Single-Particle Interpretation of the Plane (Free) Dirac Waves.- 2.3 Nonrelativistic Limit of the Dirac Equation.- Biographical Notes.- 3. Lorentz-Covariance of the Dirac Equation.- 3.1 Formulation of Covariance (Form Invariance).- 3.2 Construction of the ? Operator for Infinitesimal Lorentz Transformations.- 3.3 Finite Proper Lorentz Transformations.- 3.4 The ? Operator for Proper Lorentz Transformations.- 3.5 The Four-Current Density.- Biographical Notes.- 4. Spinors under Spatial Reflection.- 5. Bilinear Covariants of the Dirac Spinors.- Biographical Notes.- 6. Another Way of Constructing Solutions of the Free Dirac Equation: Construction by Lorentz Transformations.- 6.1 Plane Waves in Arbitrary Directions.- 6.2 The General Form of the Free Solutions and Their Properties.- 6.3 Polarized Electrons in Relativistic Theory.- 7. Projection Operators for Energy and Spin.- 7.1 Simultaneous Projections of Energy and Spin.- 8. Wave Packets of Plane Dirac Waves.- 9. Dirac Particles in ExternalFields: Examples and Problems.- 10. The Two-Centre Dirac Equation.- 11. The Foldy-Wouthuysen Representation for Free Particles.- 11.1 The Foldy-Wouthuysen Representation in the Presence of External Fields.- 12. The Hole Theory.- 12.1 Charge Conjugation.- 12.2 Charge Conjugation of Eigenstates with Arbitrary Spin and Momentum.- 12.3 Charge Conjugation of Bound States.- 12.4 Time Reversal and PCT Symmetry.- Biographical Notes.- 13. Klein's Paradox.- 14. The Weyl Equation - The Neutrino.- 15. Wave Equations for Particles with Arbitrary Spins.- 15.1 Particles with Finite Mass.- 15.2 Massless Particles.- 15.3 Spin-1 Fields for Particles with Finite Mass; Proca Equations.- 15.4 Kemmer Equation.- 15.5 The Maxwell Equations.- 15.6 Spin-$$\frac{3}{2}$$ Fields.- Biographical Notes.- 16. Lorentz Invariance and Relativistic Symmetry Principles.- 16.1 Orthogonal Transformations in Four Dimensions.- 16.2 Infinitesimal Transformations and the Proper Subgroup of O(4).- 16.3 Classification of the Subgroups of O(4).- 16.4 The Inhomogeneous Lorentz Group.- 16.5 The Conformal Group.- 16.6 Representations of the Four-Dimensional Orthogonal Group and Its Subgroups.- 16.7 Representation of SL(2,C).- 16.8 Representations of SO(3,R).- 16.9 Representations of the Lorentz Group Lp.- 16.10 Spin and the Rotation Group.- Biographical Notes.