Folk, Several errors and omissions in the description of Category 2 have been corrected. http://carnot.yi.org/Category2.xhtml Firefox and Iceweasel can display it correctly. Other browsers have problems. On one MS-Win* system, the upper half brackets are absent. Most likely a font problem. Chrome mislocates lines or arrowheads or both and fails to apply some of the text in the SVG. I'm interested in any further criticisms and suggestions. Thanks, ... Peter E. -- Google "pathology workshop". [For admin and other information see: http://www.mta.ca/~cat-dist/ ]