HI and CO Observations of Circumnebular Envelopes of Planetary Nebulae
  21cm spectral-line and continuum observations of ten compact planetary nebulae have been made with the Very Large Array. Circumnebular atomic hydrogen is identified in the planetary nebulae SwSt1, M3-35, and possibly in Hu2-1. The possibility of an inverse correlation between the optical depth of circumnebular atomic hydrogen and the linear radius of the ionised nebula is investigated, but not shown to be statistically significant. Observations of J=2-1CO emission for 22 planetary nebulae and J=3-2CO emission for 16 planetary nebulae taken with the James Clerk Maxwell Telescope are presented. J=2-1CO emission is detected in the planetary nebula M1-59, and previous CO detections in IC5117, M1-16, and NGC6302 are confirmed. J=3-2CO emission is detected in the planetary nebulae IC 5117, and NGC 6302. 
G. T. Gussie and A. R. Taylor