<Field
    ID="{61EAAF32-5837-4FEB-B278-D5FE1CC69602}"
    Name="MyTest"
    Group="My.Group"
    Type="Lookup"
    DisplayName="My Test"
    SourceID="http://schemas.microsoft.com/sharepoint/v3/fields"
    ShowField="Title"
    FieldRef ="Title"
    Required="false"
    List="Lists/My List"
    Overwrite="TRUE">
</Field>