is the four-digit year of the reference and JJJJJ
is a code indicating where the reference was published. In the case of a journal reference, VVVV
is the volume number, M
indicates the section of the journal where the reference was published (e.g., L
for a letters section), PPPP
gives the starting page number, and A
is the first letter of the last name of the first author. Periods (.
) are used to fill unused fields and to pad fields out to their fixed length if too short; padding is done on the right for the publication code and on the left for the volume number and page number.
Page numbers greater than 9999 are continued in the M
column. The 6-digit article ID numbers (in lieu of page numbers) used by the Physical Review publications since the late 1990s are treated as follows: The first two digits of the article ID, corresponding to the issue number, are converted to a lower-case letter (01 = a, etc.) and inserted into column M
. The remaining four digits are used in the page field.