| URN character | public identifier character |
| + | white space |
| : | // |
| ; | :: |
| %2B | + |
| %3A | : |
| %2F | / |
| %3B | ; |
| %27 | ’ |
| %3F | ? |
| %23 | # |
| %25 | % |
-//IDN http://ohio-state.edu/~gurari//DTD none so far//EN
urn:publicid:-:IDN+http%3A:ohio-state.edu%2F~gurari:DTD+none+so+far:EN |