DTD error problem

I have a customer who is trying to open an xml against a dtd and he continues to get the error:

C:\Users\lvian\Documents\spec2200_2011.1a\DTDs\cmm.dtd : Line: 217 Column: 66

Expected quoted string

I looked at column 66, line 217 and it says this:

<!ENTITY % ISOtech PUBLIC

"ISO 8879-1986//ENTITIES General Technical//EN" >

Looks like the string is quoted. Does anyone have any ideas on what this could be?