Group Algebras. The Green and Brauer Correspondences, the First Main Theorem. Characters, Higher Decomposition Numbers, the Second Main Theorem. Subsections, Lower Defect Groups, the Third Main Theorem. Blocks and Extensions of R. Blocks with a Cyclic Defect Group. Groups with a Sylow Group of Prime Order. The Structure of A(G). p-Solvable Groups. An Analogue of Jordan's Theorem. Types of Blocks.