Introduction

Abstract

This book arose out of a course of lectures given at the Swiss Federal Institute of Technology (ETH), Zürich, in 1966–67. The course was first set down as a set of lecture notes, and, in 1968, Professor Eckmann persuaded the authors to build a graduate text out of the notes, taking account, where appropriate, of recent developments in the subject.

Sections of this Introduction in small type are intended to give amplified motivation and background for the more experienced algebraist. They may be ignored, at least on first reading, by the beginning graduate student.