Hubble Space Telescope Measurements of the Expansion of ORGANIZATION@1 NUMBER@1 : Parallax Distance and Nebular Evolution , ORGANIZATION@2 , NUMBER@2 , NUMBER@3 The issue of how such a diverse range of nebular shapes can be produced is a controversial topic .

Hubble Space Telescope Measurements of the Expansion of ORGANIZATION@1 NUMBER@1 : Parallax Distance and Nebular Evolution , ORGANIZATION@2 , NUMBER@2 , 2430If they are n't close , there is not a good way to figure out how far away the are yet .
