Preface.- 1 Construction of Liouvillian Classes of Functions and Liouville's Theory.- 2 Solvability of Algebraic Equations by Radicals and Galois Theory.- 3 Solvability and Picard-Vessiot Theory.- 4 Coverings and Galois Theory.- 5 One-Dimensional Topological Galois Theory.- 6 Solvability of Fuchsian Equations.- 7 Multidimensional Topological Galois Theory.- Appendix A: Straightedge and Compass Constructions.- Appendix B: Chebyshev Polynomials and Their Inverses.- Appendix C: Signatures of Branched Coverings and Solvability in Quadratures.- Appendix D: On an Algebraic Version of Hilbert's 13th Problem.- References.