References

• Acker, Ochsenbein F., Stenholm B., Tylenda R., Marcout J., Schon C., 1993, The Strasbourg-ESO Catalogue of Galactic Planetary Nebulae. ESO Publishing (Acker93)
• Balick B., 1987, AJ 94, 671 NASA ADS
• Bond H.E., Livio M., 1990, ApJ 355, 568 NASA ADS
• Cahn J.H., Kaler J.B., 1971, ApJSS 22, 319 (CaKa71)
• Cahn J.H., Kaler J.B., Stanghellini L., 1992, A&AS 94, 399 (CKS92) NASA ADS
• Chevalier R.A., 1994, in Asymmetrical Planetary Nebulae, Oranim - University of Haifa, Israël, Harpaz & Soker (eds.), p. 240
• Chu Y.-H., Jacoby G.H., Arendt R., 1987, ApJS 64, 529 NASA ADS
• Dgani R., Soker N., 1997 (preprint)
• Dopita M.A., et al., 1997, ApJ 474, 188 NASA ADS
• Dopita M.A., Hua C.T., 1997, ApJS 108, 515 NASA ADS
• Drilling, 1983, ApJ 270, L13-15
• Duncan J.D., 1937, ApJ 86, 496 NASA ADS
• Dwarkadas, Balick, 1998 (preprint)
• Hua C.T., 1997, A&AS 125, 355 NASA ADS
• Hua C.T., Nguyên-Trong T., 1983, A&A 117, 272 NASA ADS
• Hua C.T., Grundseth B., Maucherat A.J., 1993, A&AS 101, 541 NASA ADS
• Jewitt D.C., Danielson B.E., Kupferman P.N., 1986, ApJ 302, 727 NASA ADS
• Kaler J.B., 1974, AJ 79, 594 NASA ADS
• Kupferman P.N., 1983, ApJ 266, 689 NASA ADS
• Kwok S., Purton C.R., FitzGerald M.P., 1978, ApJ 219, L125 NASA ADS
• Kwok S., 1982, ApJ 258, 280 NASA ADS
• Kwok S., 1994, PASP 106, 344 NASA ADS
• Livio M., 1982
• Maciel W.J., 1984, A&AS 55, 253 NASA ADS
• Meatheringham S.J., Dopita M.A., Morgan D.H., 1988, ApJ 329, 166 NASA ADS
• Millikan A.G., 1974, AJ 79, 1259 NASA ADS
• Moreno-Corral M.A., López-Molina M.G., Vásquez-R G.A., 1992, Rev. Mexicana Astron. Astrof. 24, 151 NASA ADS
• Pascoli G., 1992, PASP 104, 350 NASA ADS
• Peimbert M., 1981, in Physical Processes in Red Giants? Reidel Publ., Iben Jr. & Renzini (eds.), p. 409
• Peimbert M., Torres-Peimbert S., 1983, IAU Symposium 103. London, Reidel, Dordrecht
• Pottasch S.R., 1984, Planetary Nebulae. Reidel, Dordrecht
• Pottasch S.R., 1989, A&A 205, 248 NASA ADS
• Renzini, 1981, Physical Processes in Red Giants. D. Reidel Publ.
• Schwarz H., Corradi R., Melnick J., 1992, A&AS 96, 23 NASA ADS
• Shklowskii I.S., 1956, Astron. Zh. 33, 315
• Stewart, 1898, Harvard Annals 60, 163
• Tüg H., 1975, AAS 39, 67
• Vassiliadis E., Wood P.R., 1994, ApJSS 92, 125
• Warner J.W., 1974, PASP 86, 885 NASA ADS
• Zhang C.Y., 1988, Ph.D. Thesis
• Zhang C.Y., Kwok S., 1998, ApJS (in press)