Electronic location and access
856 41 ‡3 Abstracts and index ‡u http://…
856 42 ‡z Publisher's home page: ‡u http://…
The 856 can be used to cite the location of partial contents of the resource cataloged, such as summaries, abstracts, or tables of contents.
Second indicator "1" and $3 are used to show this:
For related resources that do not represent the serial cataloged, its online version, or a part of the serial.
Use second indicator "2."