Ours
                  New   Old   O'D62  Hynes Ma84  Cahn92 VdS94 Po96  Ha97 NOAO

M27  NGC 6853     1.25  1.25  0.85   0.8   1.3   0.854  1.3   1.17  1.24  0.85
M57  NGC 6720     2.3   4.1   2.20         2.28  2.84   3.26  1.63  2.30  3.00
M76  NGC  650-1   3.4   3.4   1.75               2.41   4.24  2.35        2.50
M97  NGC 3587     2.6   2.6   1.62               2.00   3.88  1.79        2

O'D62

Charles Robert O'Dell, 1962. A distance Scale for Planetary Nebulae Based on Emission-Line Fluxes. Astrophysical Journal, vol. 135, p. 371-384 (03/1962)

Ma84

Maciel W., 1984. A catalogue of distances of planetary nebulae. Astron and Astrophys Supp, 55, 253.

Cahn92

Cahn, J. H.; Kaler, J. B.; Stanghellini, L., 1992. A catalogue of absolute fluxes and distances of planetary nebulae. Astronomy and Astrophysics Supplement Series , vol. 94, no. 3, Sept. 1992, p. 399-452.

VdS94

Van De Steene, G., Zijlstra A., 1994. On an alternative statistical distance scale for planetary nebulae. Catalog with statistical distances to planetary nebulae. Astron and Astrophys Supp, 108, 485.

Po96

Pottasch, S.R., 1996. Local space density and formation rate of planetary nebulae. Astronomy and Astrophysics, 307, p. 561-578.

Ha97

Harris, H.C., Dahn, C.C., Monet, D.G., and Pier, J.R., 1997. Trigonometric parallaxes of Planetary Nebulae. In H.J. Habing and H.J.G.L.M. Lamers (eds.), Planetary Nebulae. IAU Symposium No. 180, p. 40-45.

NOAO

N.A. Sharp et.al.. NOAO Website