bib entries exported from http://adsabs.harvard.edu sometimes the field
archivePrefix is missing. One example is this paper: http://adsabs.harvard.edu/abs/2003A%26A...410..389R
As a result of the missing prefix, the hyperlink to the preprint is build incorrectly and does not work.
Of course I could add it manually each time, but as this effects roughly 20% of the ADS preprints (based on the limited and maybe biased survey of papers I cite in my work) I'd like to have some workaround.