The Publisher Item Identifier (PII) is a unique identifier used by a number of scientific journal publishers to identify documents. [1] It uses the pre-existing ISSN or ISBN of the publication in question, and adds a character for source publication type, an item number, and a check digit.
The system was adopted in 1996 by the American Chemical Society, the American Institute of Physics, the American Physical Society, Elsevier Science, and the IEEE.
A PII (pii) is a 17-character string, consisting of:
When a PII is printed (as opposed to stored in a database), the 17-character string may be extended with punctuation characters to make it more readable to humans, as in Sxxxx-xxxx(yy)iiiii-d or Bx-xxx-xxxxx-x/iiiii-d.