The links to MIRIAM Resources in the SBML specification Level 2 Version 4 Release 1 are obsolete.
The obsolete links look like: http://www.ebi.ac.uk/compneur-srv/miriam-main/
These are present in the following sections:
- 6.4 "Use of URIs" (page 94 of the PDF version)
- 6.5 "Relation elements" (page 95 of the PDF version)
I would suggest to use this link instead: http://www.ebi.ac.uk/miriam/