1. Introduction  
2. VLBA Observations and Data Reduction  
2.1. Sample Selection  
2.2. Observations  
2.3. Data Reduction  
2.4. Model Fitting  
3. Results  
3.1. VLBA Images  
3.2. Parsec-scale Morphology  
3.3. Comments on Selected Individual Sources  
4. Discussion  
4.1. Source Compactness  
4.2. Core Brightness Temperature  
4.3. Correlation Between Radio and Gamma-ray Emission  
5. Summary