Introduction

1 Introduction

2 Galaxy redshift surveys

2.1 Important point on evolution bias

2.2 Simple luminosity function models

2.3 Hα survey (Euclid-/Roman-like)

3 Galaxy surveys with K-correction

3.1 Bright galaxy survey (DESI-like)

4 21cm HI surveys

4.1 HI galaxy surveys (SKAO-like)

5 Conclusions