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Table of Contents

TITLE PAGE

1.INTRODUCTION

2.RING GALAXIES

3.OUTER RINGS AROUND SPIRALS AND S0s

4.POLAR RING GALAXIES
4.1.Observational Properties
4.2.Theoretical Considerations
4.3.Gas Around S0s

5.SHELLS AROUND ELLIPTICAL GALAXIES
5.1.Shells, and Ripples
5.2.Theories of Shell Formation
5.3.The Problem of Dust and Gas

6.FINAL REMARKS

REFERENCES