1. Introduction
2. Observations and Data Analysis
2.1. Sample Selection
2.2. Observations
2.3. Data Reduction
2.4. Telluric Lines
3. Radial Velocity Measurement
3.1. Model Atmospheres
3.2. FITSB2 and the Fit Process
4. Results
4.1. Peculiarities
4.2. Detection Efficiency
4.3. DA White Dwarfs with Ca II Lines
4.4. Double Degenerates
4.5. Notes on Individual Objects
4.6. Comparison with Maoz & Hallakoun (2017)
5. Discussion
5.1. Dependence of DD Numbers on Mass
5.2. Selection Effects in the SPY Sample
5.3. Implications for SN Ia Progenitor Scenarios
6. Summary