DOCBOOK-APPS: publisher element

hi guys,

can anybody help me about this?

My text shows like this: "Philadelphia: WB Saunders,"

with error:
<publisher>
	<address>
		<city>Philadelphia:</city>
	</address>
	<publishername>WB Saunders,</publishername>
</publisher>

valid:
<publisher>	
	<publishername>WB Saunders,</publishername>
	<address>
		<city>Philadelphia:</city>
	</address>
</publisher>

Is there anybody know the reason behind this?

thanks,
restie