Abundances of planetary nebulae NGC 7662 and NGC 6741 S. R. Pottasch, D. A. Beintema, J. Bernard Salas and W. A. Feibelman A&A, 380 2 (2001) 684-694 Published online: 15 December 2001 DOI: 10.1051/0004-6361:20011480