Planetary nebulae: abundances and abundance gradients

In this work, a review is given of some recent results and problems involved in the determination of chemical abundances of galactic planetary nebulae, particularly regarding disk and bulge objects

PLANETARY-NEBULAE NEAR THE GALACTIC-CENTER .3. THE WSRT MEASUREMENTS

We report the detections of radio continuum emission at 6 cm from 74 IRAS sources with a typical far infrared color of planetary nebulae, located within 15 degrees of the galactic center