19.4 Non-alphabetical order
Some matter will call for ordering on some basis other than alphabetical, such as numerical, chronological, or hierarchical. Where this matter forms part only of an occasional group of subentries within an otherwise alphabetical index it may be ordered as necessary without comment; however, where a significant amount needs to be included in the form of headings it should be placed in a separate index where similar elements can be found and compared easily. Never arrange entries or subentries themselves by order of locator, as this is of least help to the reader.
Chronological ordering may be useful in arranging entries or subentries, for example according to the life and times of the subject in a biography:
Legendary Period (prehistoric) 1–33, 66, 178
Xia (c.2100–1600 bc) 35–60, 120
Shang (c.1600–c. 1027 bc) 61–84
Zhou (c.1027–256 bc) 12, 85–100, 178
Quin (221–207 bc) 109–35
Han (206 bc–ad 220) 132,136–7, 141
apprenticeship 192, 195
in London 195–9
in Oxford 200, 201–60
illness and death 208, 277–9
Subjects may sometimes be ordered according to some recognized hierarchical system of classification (e.g. BA, MA, MPhil, DPhil or duke, marquess, earl, viscount, baron). Indexes of scriptural references are arranged in their traditional order rather than alphabetically.