You may need to try searching both ways. Some older material has a PC number,eg. If a periodical article is on a required reading list, it will have beenphotocopied for the ReserveCollection. Occasionally periodical articles on Reserve are not indexed by author. Periodical articles on Reserve will usually have a photocopy number, beginning with the topic code, followed by an item number, eg.
Some older material has a PC number, eg.
PC5239 Apart from photocopied material, you can't search for a periodical article on Investigator. If you have a reference for a periodical article which is not on a reading list you will need to locate it in the appropriate issue of the periodical itself. This means doing a Periodical title search. See the section Periodicals for how to do this. Notethe full number for that item, eg.