The man pages for pbmclean, pbmpscale, pbmtopgm and pnmpad all have
a .TH macro of the form '.TH pbmclean "12 Dec 1990"' which is missing
the man page section number.  The correct line should read
'.TH pbmclean 1 "12 Dec 1990"'.

This is obvious looking at the man page as it appears with the date
where the section should be.  This was discovered while writing a tool
to attempt to extend upon apropos.