xsd Schema and ref groups

Hi..
I have a little trouble defining a group in my xsd schema.

I have a tag in my xml which have some sub elements
eks:

<TEST>
    <ELEM1>
    <ELEM2>
    <ELEM3>
</TEST>

How do i define in my xsd schema that any element (ELEM1/2/3), can accour any number of times, in any order and none of them are required.

I cant use: <xsd:sequence> because they can come in any order,
I cant use: <xsd:choice> because all elements can be there
I cant use: <xsd:all> because its not required that all of them have to be there.

How do i do that ?