A complete description of the reference coding has been published as a chapter of the book "Information & On-Line Data in Astronomy", 1995, D. Egret and M. A. Albrecht (Eds), Kluwer Acad. Publ. (also available as a Postcript file or as a PDF document).
You can obtain here the complete and up-to-date list of Journal reference codes.
The bibliography is updated on a daily basis, thanks to the efforts of the librarians of the Institut d'Astrophysique de Paris (IAP) and of the Observatories of Paris, Bordeaux and Strasbourg.