Keywords:  galaxies: active — galaxies: nuclei — quasars: general — quasars: emission lines

1. INTRODUCTION

2. DATA AND DATA PROCESSING

2.1. The Quasar Sample

2.2. Spectroscopic Data

2.3. Photometric Data

2.4. Light Curve Inter-Calibration and Uncertainty Corrections

2.5. Emission-Line Variability Contamination

3. TIME-SERIES ANALYSIS

3.1. Lag Measurements

3.2. Alias Identification and Removal

3.3. Lag-Significance Criteria

4. RESULTS AND DISCUSSION

4.1. Lag Results

4.2. The C IV Radius-Luminosity Relation

4.3. Black-Hole Mass Measurements

5. SUMMARY