...
856 40 $3 Current issues available from the Publications Page of the ASA Web site $u http://www.asanet.org/pubs/pubs.html
On the record for a print (or other format) serial to cite the location of partial contents or related information, such as summaries, abstracts, tables of contents, or subscription information. Subfield $3 should be used to note the part that is online. Use second indicator “1” whenever the URI points to any part of the electronic manifestation.
856 41 $3 Summaries and index $u http:// ...
For related resources that do not represent the serial cataloged, its online manifestation, or a part of the serial. Common examples would be an organizational home page or publisher's website. If an organizational home page contained a 10-year index to a journal or the tables of contents of several titles, this would be a related website. Use second indicator “2.”
...