pressure in the nebulae caused by photo-ionization or fast winds. In the case of the CO lines, the large line widths of the PN spectra in Fig. 1 are mostly formed by extended line wings, e.g., M 1-59 (023.9$-$02.3). Similar wings are commonly seen in proto-PNe before the onset of ionization, and in the few cases of young PNe where the CO line wings have been studied at high angular resolution, e.g., M 1-16 (Huggins et al. 2000) and He 3-1475 (Huggins et al. 2004), it is found that the wings arise from molecular gas entrained in the sides of high velocity jets. Thus although the kinematics of the molecular gas may be affected by thermal pressure in the ionized gas, the frequency with which wings are seen in the CO spectra reported here probably reflects the frequency of jets in PN formation.

In a few of the cases reported here, the whole CO line appears to be broadened. The most extreme case is K 3-17 (039.8+02.1) which shows a steep-sided, roughly flat-topped profile (with some IS contamination near the center) that is 90 [kms$^{-1}$]{} wide. This profile is unique among PNe and the object deserves further study.

Conclusions
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