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Published online by Cambridge University Press: 26 May 2016
We have constructed photoionization models of NGC 6153, M 2–36, and M1–42. These planetary nebulae show large differences, both, in the CNO and Ne abundances as derived from recombination lines and collisionally excited lines, as well as, in the electron temperature determined from Balmer jump and [OIII] lines. The model nebulae have low mass (about 1% of the total nebular mass) inclusions where the CNO and Ne abundances are enhanced by a factor of 200 or so.