XSD.Exe ignoring certain elements

[eSapient]

For the following XSD:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xs:element name="E1" type="CT1"/>
<xs:complexType name="CT1">
<xs:sequence>
<xs:element name="CT1_E1"
type="xs:string"/>
<xs:choice>
<xs:sequence>
<xs:element
name="CT1_E2" type="xs:string"/>
<xs:element
name="CT1_E3" type="xs:string"/>
</xs:sequence>
<xs:group ref="G1"/>
</xs:choice>
</xs:sequence>
</xs:complexType>
<xs:group name="G1">
<xs:choice>
<xs:element name="G1_E1"
type="xs:string"/>
<xs:element name="G1_E2"
type="xs:string"/>
</xs:choice>
</xs:group>
</xs:schema>

XSD.Exe generated the following code:

using System.Xml.Serialization;

[System.Xml.Serialization.XmlRootAttribute("E1",
Namespace="", IsNullable=false)]
public class CT1 {
public string CT1_E1;

[System.Xml.Serialization.XmlElementAttribute
("CT1_E3", typeof(string))]
[System.Xml.Serialization.XmlElementAttribute
("CT1_E2", typeof(string))]
[System.Xml.Serialization.XmlChoiceIdentifierAttrib ute
("ItemElementName")]
public string Item;

[System.Xml.Serialization.XmlIgnoreAttribute()]
public ItemChoiceType ItemElementName;
}

[System.Xml.Serialization.XmlTypeAttribute
(IncludeInSchema=false)]
public enum ItemChoiceType
{
CT1_E3,
CT1_E2,
}

I don't see any reference to the group <G1> or its
elements <G1_E1> and <G1_E2>. How am I supposed to work
with <G1_E1> and <G1_E2>?

Any help would be greatly appreciated.