Category: atom_site
Data type: char
Must appear in a looped list
containing '_atom_site_label'
Must match a value of '_cell_subsystem_code'
A code that links a given atom or rigid-group site to one of the subsystems present in a composite. This code provides an alternative description for composites less explicit than that based on linked data blocks (see the description in this dictionary of _audit_link_[ms]). It must match one of the labels specified for _cell_subsystem_code.