Operator groups

Hi,

I'm writing an XSLT stylesheet to transform equations from an older,
SGML markup into presentation MathML.

I noticed that <mrow> elements should be used to group sub-expressions
(3.3.1.3) and, specifically, that a nested <mrow> is not needed when
all the operators are from the same group in the Operator Dictionary.

So I looked at Appendix F, where it says, "The operators are divided
into groups, which are separated by blank lines in the listing below."
Unfortunately, when I look at the list of entries (F.5), I cannot see
any blank lines.

Is this an error (I can't see it in the errata)?  Or should I take it
that all operators are in the same group (in which case why make the
distinction) and ignore the recommendation to nest?

I would be very grateful if anybody can clarify this point, or refer
me to a correctly grouped operator dictionary.

Regards,

Martin Dransfield
Elsevier Science