Shocked Molecular Gas in the Supernova Remnant HB 21
  We report the discovery of the shocked molecular gas in the supernova remnant HB 21. We derive the physical parameters of the shocked gas from CO J=1-0 and J=2-1 line observations. We discuss the correlation of the shocked molecular gas with the previously detected, shocked atomic gas and the associated infrared emission. 
Bon-Chul Koo, Jeonghee Rho, William T. Reach, JaeHoon Jung, Jeffrey G.   Mangum