In general, characters with cedillas or ogoneks below are subject to variable typographical usage, depending on the availability and quality of fonts used, the technology, and the geographic area. Various hooks, commas, and squiggles may be substituted for the nominal forms of these diacritics below, and even the direction of the hooks may be reversed. Implementations should take care to become familiar with particular typographical traditions before assuming that characters are missing or are wrongly represented in the code charts in the Unicode Standard.
This seems straighforward, but perhaps something about varrying use in linguistic tradition might be added.
ALso this passage and some of the other discussion about diacritics might better appear in section 7.9 "Combining Marks" with a cross-reference in 7.1.
The character h-ogonek is used is Avestan transliteration according to the system shown at http://www.avesta.org/avencode.html. The characters n-ogonek and t-ogonek also appear here.
John Cowan includes SMALL C WITH OGONEK in a list of characters at http://mercury.ccil.org/~cowan/elsie/elsie.txt.
Jim Allan
