1. Introduction  
2. Description of the sample  
3. The data  
3.1. Interferometric data  
3.2. Additional mid-IR spectra  
3.3. Mid-IR variability  
4. SED fitting  
5. Interferometric model fitting  
5.1. The models  
5.2. The fit strategy  
5.3. The fit results  
6. Notes on some individual targets  
7. Sample analysis  
7.1. The half-light radius  
7.2. Brightness temperatures  
7.3. A size-color relation  
8. Comparison with a RT model grid  
8.1. The RT grid  
8.2. Model comparison  
8.3. Comparison with YSOs  
9. Discussion  
9.1. Aspect angle  
9.2. Comparison with YSO  
9.3. Binary connection  
9.4. Formation and evolution  
9.5. Conclusion