Referring to author order on paper when arXiv and published copy are different A paper that I need to refer to reasonably often has in its arXiv version the authors listed alphabetically by surname (as is the custom in mathematics). The published version lists the authors in a different order, having moved the last author to second place. The last author in the published version is  recently told me he doesn't understand why people keep insisting on using the published author order (or to put it bluntly: why they keep listing him last).

What would be the correct way to refer to the joint work, given that the arXiv version is no less prominent than the published version? (Other than in the bibliography, where I would stick to the published order) I'm not sure whether it is more accurate to talk about the work/results of ABCD or of ADBC.
As Aaron Montgomery's answer states, if you use the full author list in the text, it should match the author list in the bibliography. However, with four authors, you're usually in a position where you can just say 


  A et al.


in the text rather than


  A, B, C, and D


or 


  A, D, B, C