1<!DOCTYPE doc [ 2<!ELEMENT doc (a, b, c, b, c, d) > 3<!ELEMENT a EMPTY> 4<!ELEMENT b EMPTY> 5<!ELEMENT c EMPTY> 6<!ELEMENT d EMPTY> 7<!ENTITY c "<c/>"> 8<!ENTITY bc "<b/>&c;"> 9]> 10<doc> 11<a/> 12&bc; 13&bc; 14<d/> 15</doc> 16