Hierarchical Structure of HII Regions - Ultracompact, Compact, and   Extended Components
  We have observed extended emission physically associated with 15 out of 16 UC HII regions with large ratios of single-dish to VLA fluxes. We discuss their implications for the age problem of UC HII regions and the evolution of HII regions. 
Kee-Tae Kim and Bon-Chul Koo (Seoul National University)