  Interstellar medium clouds in the W28 region are emitting gamma-rays and it
is likely that the W28 supernova remnant is responsible, making W28 a prime
candidate for the study of cosmic-ray acceleration and diffusion. Understanding
the influence of both supernova remnant shocks and cosmic rays on local
molecular clouds can help to identify multi-wavelength signatures of probable
cosmic-ray sources. To this goal, transitions of OH, SiO, NH3, HCO+ and CS have
complemented CO in allowing a characterization of the chemically rich
environment surrounding W28. This remnant has been an ideal test-bed for
techniques that will complement arcminute-scale studies of cosmic-ray source
candidates with future GeV-PeV gamma-ray observations.
