帮我检查一下这个XML的错误 - Web 开发 / XML/SOAP

这个XML总是报这个错：Open quote is expected for attribute "{1}" associated with an element type "using".
为什么？
XML code:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE databases [
<!ELEMENT databases (database+)>
<!ATTLIST databases
using IDREF #REQUIERD
>
<!ELEMENT database (driver,url,userName,password)>
<!ATTLIST database
id ID #REQUIERD
>
<!ELEMENT driver (#PCDATA)>
<!ELEMENT url (#PCDATA)>
<!ELEMENT userName (#PCDATA)>
<!ELEMENT password (#PCDATA)>

]>
<databases using="mysql">
<database id="mysql">
<driver>com.mysql.jdbc.Driver</driver>
<url>mysql://localhost:3306/test</url>
<userName>root</userName>
<password>sss</password>
</database>
<database　id="sqlserver">
<driver>com.microsoft.sqlserver.jdbc.SQLServerDriver</driver>
<url>sqlserver://ip:port;database=DBName</url>
<userName>sa</userName>
<password>sss</password>
</database>
</databases>

---

第二个
<database id="sqlserver">

中间的字符错了，应该是空格