1 INTRODUCTION

2 H-ALPHA PHYSICS: FROM SFR TO LINE LUMINOSITY

3 MODELLING H-ALPHA EMISSION

4 SIMULATED H-ALPHA EMISSION FROM GALAXIES AND FROM THE IGM

5 SURVEYS OF H-ALPHA EMISSION

6 CONTAMINATION IN H-ALPHA OBSERVATIONS

7 ALTERNATIVE FOREGROUND REMOVAL/AVOIDING METHODS

8 ASTROPHYSICAL CONSTRAINTS FROM GALAXY SURVEYS VERSUS IM SURVEYS

9 SUMMARY AND DISCUSSION