4.3.1 Format of background art citations 

In citing documents or inserting references, applicants and examining divisions alike must use codes that allow the references to be retrieved without difficulty. This can be best achieved through consistent use of the WIPO standards format:

(i)for non-patent literature, WIPO Standard ST.14 (Recommendation for the Inclusion of References Cited in Patent Documents); 

(ii)for patent literature (applications, granted patents and utility models): for the two-letter country code, WIPO Standard ST.3 (Recommended Standard on Two-Letter Codes for the Representation of States, Other Entities and Intergovernmental Organizations); for symbols indicating the type of document, WIPO Standard ST.16 (Recommended Standard Code for the Identification of Different Kinds of Patent Documents). 

WIPO standards:

ST.14 (http://www.wipo.int/export/sites/www/standards/en/pdf/03-14-01.pdf)
ST.3 (http://www.wipo.int/export/sites/www/standards/en/pdf/03-03-01.pdf)
ST.16 (http://www.wipo.int/export/sites/www/standards/en/pdf/03-16-01.pdf)

These can be found on the WIPO website.

However, in the case of deviation from these standards there is no need to correct the codes used, as long as straightforward retrieval of the citation(s) is possible.