A handy reference for phonetic symbols, which covers both IPA and other
common uses, is Geoffrey K. Pullum and William A. Ladusaw's "Phonetic
Symbol Guide," Chicago: University of Chicago, 1986.
P. 204 points out that macron (whose name, after all, implies length) is
recommended by the IPA as a specific tone mark, but that it is used very
widely to represent length.
Macron is commonly written over long syllabic sonants, including m, by
Because length is represented variously in printed sources, it might be
useful to encode it as markup (something like <long>m</long>), which
would simplify rendering it as a superscript macron or a following colon
or however else a particular rendering may require.
Professor David J. Birnbaum [log in to unmask]
The Royal York Apartments, #802 http://clover.slavic.pitt.edu/~djbpitt/
3955 Bigelow Boulevard voice: 1-412-624-5712
Pittsburgh, PA 15213 USA fax: 1-412-624-9714