When the index is converted to HTML, the composite page numbers are used to construct file names and Uniform Resource Locators (URLs). Parentheses and en-dashes are discarded from the composite page numbers, and slashes and hyphens are added to separate the parts.
Paired question marks (?? ), which indicate unknown values, are converted to xx in order to produce portable file names, which is important because the bibliographic data is mirrored to several other sites with different operating systems. No attempt is made, however, to shoehorn them into the grossly-inadequate 8+3-character filename limitation of IBM PC DOS. Most users of IBM PC machines now run a windowing operating system with better support for long filenames, and PC DOC machines are unlikely to be used as Web servers, so I do not apologize for this decision.
In the event that multiple BibTEX entries have the same volume, number, and pages values, which can happen for very short articles in some journals and periodicals, or in cases where those values are not yet known, a fifth number is suffixed to the composite page number to make it unique. The HTML form of the index may therefore contain composite page numbers that look like 105(3)xx-xx-3, which would have a corresponding file named 105/3/xx-xx-3.html.