References

• Aller L.H., 1982, ASS 83, 225
• Balick B., Preston H.L., Icke V., 1987, AJ 94, 1641 NASA ADS
• Balick B., Perinotto M., Maccioni A., Terzian Y., Hajian A., 1994, ApJ 424, 800 NASA ADS
• Balick B., Rugers M., Terzian Y., Chengalur J.N., 1993, ApJ 411, 778 NASA ADS
• Boeshaar G.O., 1974, ApJ 187, 283 NASA ADS
• Boffi F.R., Stanghellini L., 1994, A&A 284, 248 NASA ADS
• Bohigas J., 1994, A&A 288, 617 NASA ADS
• Cahn J.H., Kaler J.B., Stanghellini L., 1992, A&AS 94, 399 NASA ADS
• Capriotti E.R., 1973, ApJ 179, 495 NASA ADS
• Corradi R.L.M., Schwartz H.E., 1995, A&A 293, 871 NASA ADS
• Cuesta L., Phillips J.P., Mampaso A., 1993, A&A 267, 199 NASA ADS
• Cuesta L., Phillips J.P., Mampaso A., 1995, A&A 304, 475 NASA ADS
• Goodrich R.W., 1991, ApJ 376, 654 NASA ADS
• Gruenwald R.B., Viegas S.M., 1992, ApJS 78, 153 NASA ADS
• Harrington P., 1995, STScI Press Release STScI-PRC95-01
• Hartigan P., Raymond J., Hartmann L., 1987, ApJ 316, 323 NASA ADS
• Hyung S., Aller L.H., 1996, MNRAS 278, 551 NASA ADS
• Hyung S., Aller L.H., 1995, MNRAS 273, 973 NASA ADS
• Hyung S., Aller L.H., Feibelman W.A., 1994, MNRAS 269, 975 NASA ADS
• Hyung S., Keyes C.D., Aller L.H., 1995, MNRAS 272, 49 NASA ADS
• Icke V., Balick B., Frank A., 1992, A&A 253, 224 NASA ADS
• Icke V., Preston H.L., 1989, A&A 211, 409 NASA ADS
• Kaler J.B., Browning L.B., Shaw R.S., 1996, A Catalog of Relative Emission Line Intensities in Planetary Nebulae
• Kastner J.H., Gatley Y., Merrill K.M., Probst R., Weintraub D.A., 1994, ApJ 421, 600 NASA ADS
• Kastner J.H., Weintraub D.A., Gatley Y., Merrill K.M., Probst R., 1996, ApJ 462, 777 NASA ADS
• Kimeswenger S., 1997, The Data Base of Galactic PNe in Innsbruck, Institute of Astronomy, Innsbruck
• Kingsburgh R.L., Barlow M.J., 1992, MNRAS 257, 317 NASA ADS
• Kingsburgh R.L., English J., 1992, MNRAS 259, 635 NASA ADS
• Köppen J., 1979, A&A 80, 42 NASA ADS
• Köppen J., 1983, A&A 122, 95 NASA ADS
• Lopez J.A., Vazquez R., Rodriguez L.F., 1995, ApJ 455, L63 NASA ADS
• Mallik D.C.V., Peimbert M., 1988, Rev. Mex. A&A 16, 111
• Manchado A., Guerrero M.A., Stanghellini L., Serra-Ricart M., 1996, IAC Morphological Catalog of Northern Galactic Planetary Nebulae, IAC
• Meaburn J., Walsh J.R., 1980a, MNRAS 257, 628
• Meaburn J., Walsh, J.R., 1980b, MNRAS 193, 631 NASA ADS
• Middlemass D., 1990, MNRAS 244, 294 NASA ADS
• O'Dell C.R., Handron K.P., 1996, STScI Press Release STScI-PR96-13
• Peimbert M., Torres-Peimbert S., 1983, in Planetary Nebulae, IAU Symp. 103, Flower (ed.), p. 233
• Perek L., Kohoutek L., 1967, Catalogue of Galactic Planetary Nebulae, Academa Publ. House, Czechoslovak Academy of Sciences
• Phillips J.P., 1989, in: Planetary Nebulae, IAU Symp. 131, Torres-Peimbert S. (ed.), p. 425
• Phillips J.P., 1997, A&A (in press)
• Phillips J.P., Reay N.K., 1980, Astrophys. Lett. 21, 47 NASA ADS
• Phillips J.P., Williams P.G., Mampaso A., Ukita N., 1992, ASS 188, 171
• Pottasch S.R., 1984, Planetary Nebulae. D. Reidel Publishing Co., Dordrecht, Holland
• Raymond J.C., Hartigan P., Hartmann L., 1988, ApJ 326, 323 NASA ADS
• Reay N.K., Walton N.A., Atherton P.D., 1988, MNRAS 232, 615 NASA ADS
• Rowlands N., Houck J.P., Hertier T., 1994, ApJ 427, 867 NASA ADS
• Savage B.D., Mathis J.S., 1979, ARA&A 17, 73 NASA ADS
• Schwartz H.E., Corradi R.L.M., Melnick J., 1992, A&AS 96, 23 NASA ADS
• Schonberner D., 1979, A&A 79, 108 NASA ADS
• Schonberner D., 1981, A&A 103, 119 NASA ADS
• Schonberner D., 1983, A&A 272, 708
• Shull M.J., McKee C.F., 1979, ApJ 227, 131 NASA ADS
• Trammell S.R., Goodrich R.W., 1996, ApJ 468, L107 NASA ADS
• Tylenda R., Acker A., Stenholm B., Köppen J., 1992, A&AS 95, 337 NASA ADS
• Webster B.L., Payne P.W., Storey J.W.V., Dopita M.A., 1988, MNRAS 235, 533 NASA ADS
• Zuckerman B., Gatley Y., 1988, ApJ 324, 501 NASA ADS