The non-fiction contents of the GOP are both more important, and more difficult to classify, than the fiction contents. A series of articles on one main topic may have very different titles, while other titles give little clue to the contents of the article. The name of the author, however, is usually of importance, for research purposes and for general interest, and so the index was originally sorted by author. The current Index, however, allows the entries be to searched and sorted by title, author, volume and year of publication. The Author Index can also be searched for authors of non-fiction articles.
It was also decided to allocate a "subject" category to each article. A list of these arbitrary headings, with their code letters, can be found here. Non-fiction articles can be searched and sorted by their subject category.
Each entry in the Index comprises a single article published in a single volume. However, since a number of articles were published over more than one volume, a particular article may have multiple entries. For ease of reference, these multiple entries will normally be grouped together under the one title. Please note, however, that sorting the entries by volume will break up this grouping.
The Index contains a number of cross-referencing links. To see all entries by the author of an article, click on the author's name. To see all entries in the same volume or year of publication, click on the volume number or year. To see all entries in the same subject category, click on the subject code letter.