1<!ENTITY % b SYSTEM "http://example.org/b/b.dtd"> 2%b; 3<!ENTITY % a SYSTEM "http://example.org/a/a.dtd"> 4%a; 5<!ENTITY % c SYSTEM "http://example.org/c/c.dtd"> 6%c; 7<!ELEMENT bac (b, a, c)> 8